The Dragon Balls

The Dragon Balls are a Namekian creation. As stated by the Elder Namekian in DB 265, they are the 'spheres of hope...the proof of the wisdom and strength of the children of Namek'. There exist three different sets of Dragon Balls. They can grant the power of wishes to whomever gather all seven, but the appearance, size, and the restrictions on the wishes possible differ from set to set.

Listed below are the three sets of Dragon Balls: the Earthen balls, the Namekian balls, and the Black Star balls. It should be noted that the Earthen balls are unique in that most of the wishes we see in Dragon Ball/Z create evil dragons that emerge much later, around the time of Dragon Ball GT!

A red wish indicates that the wish was made in both the anime and the manga. A green wish indicates that the wish was only made in the anime/movies.

Earthen Dragon Balls

Seen in:
Dragon Ball, Dragon Ball Z, Dragon Ball GT

Dragon:
Shenlong (Traditional Chinese Dragon)

Creator/Maintainer:
First set created/maintained by God pre-joining of Piccolo (Devil) and God. Second set created/maintained by Dende.

Appearance:
Red stars within orange balls.

Size:
Smallest of all of the balls.

Restrictions for all of Dragon Ball, up to the rejoining of Piccolo (Devil) and God:
You have only one wish. (Stated several times. IE, Shenlong in DB 212)
You cannot wish for more wishes. (Where stated...?)*
You cannot make a wish that exceeds the power of the creator of the Dragon Balls. (Stated by Shenlong in DB 212)
You cannot revive anyone who has been dead for more than a year. (Stated by God in DB 321)
You cannot revive someone twice. (Stated/implied by Goku in DB 198)
You cannot wish back those who have died naturally. (Stated by God in DB 321)
If the creator of the Dragon Balls dies or ceases to exist, then the Dragon Balls themselves cease to exist. (Proven by the death of God/Piccolo in DB 223 and the rejoining of Devil and God in DB 360)
If the creator of the Dragon Balls is revived, then the Dragon Balls will exist once more. (Proven by Piccolo's statement in DB 293)
The maintaining of the Dragon Balls can be passed onto another individual. (Proven by Dende's creation of new Dragon Balls in DB 393)
Each wish made creates negative energy inside the balls. Too many wishes creates an overload of negative energy, which will result in the Dragons themselves emerging. (Stated by Dark Shenlong in DBGT Episode 48)

Restrictions after Dende becomes the new God of Earth:
You can only have two wishes. However, you may use one wish and wait only four months to make the second. (Stated by Yamcha. DB ?)
Other restrictions remain the same, or can be presumed to remain the same.

Wishes used:
"Pilaf"
When?: After everyone has been captured by Pilaf. Oolong and Pu'ar have escaped.
Wishmaker?: Oolong
Created?: Six-Star Dragon
1. Get the softest pair of panties in the world.

"Red Ribbon/Uranai Baba"
When?: After the defeat of the Red Ribbon and Pilaf's attack.
Wishmaker?: Son Goku
Created?: Two-Star Dragon
1. Revive Bora, Upa's father.

10th Anniversary Movie
When?: After the defeat of Black.
Wishmaker?: Son Goku
1. Recreate Android 8, aka Ha-chan.

"Piccolo Daimao"
When?: After the death of Kame'Sennin.
Wishmaker?: Piccolo Daimao
Created?: Four-Star Dragon
1. Grant Piccolo Daimao eternal youth.

"Piccolo Daimao"
When?: After Piccolo Daimao's defeat.
Wishmaker?: Son Goku?
1. Revive all those killed by Piccolo Daimao or his children.

Movie 1: Garlic Jr
When?: After the 23rd Tenkai'chi Budokai, and before Radditz arrives.
Wishmaker?: Garlic Jr
1. Grant Garlic Jr immortality.

"The Saiyans"
When?: The day before the arrival of Vegita and Nappa.
Wishmaker?: Kame'Sennin
Created?: Five-Star Dragon
1. Revive Son Goku.

Movie 2: Dr. Willow
When?: Sometime after Kaio's training, but before Namek.
Wishmaker?: Dr. Kochin
1. Remove the ice barriers that exist around Dr. Willow's laboratory.

Movie 3: Tales
When?: Sometime after Kaio's training, but before Namek.
Wishmaker?: Gohan
1. Recreate the forest that was burnt up by falling 'meteors'.

Movie 4: Slug
When?: Sometime before/after Goku's non-SSj battle with Freeza.
Wishmaker?: Slug
1. Grant Slug eternal youth.

"Freeza"
When?: During Goku and Freeza's final battle.
Wishmaker: Mr. Popo.
Created?: One-Star Dragon
1. Revive all those killed by Freeza or his soldiers.

"Cell"
When?: After Cell's defeat.
Wishmaker: Yamcha (for first). Kuririn (for second).
1. Revive Cell's victims.
2. Remove the explosives from the bodies of the Artificial Humans.

Movie 10: Broly's Return
When?: During the final struggle with Broly on Earth.
Wishmaker: Goten?
1. Bring Goku back to Earth to help stop Broly.
(The second wish is never elaborated on.)

"Majin Buu"
When?: After the Majin Vegita events and the emergence of Buu.
Wishmaker?: Bulma
Created?: Seven-Star Dragon
1. Revive all of the people killed by Majin Vegita in the Tenkai'chi Budokai, save the 'evil ones'.

Movie 12: Janemba
When?: During the Majin Buu events, but before the Earth's population is eradicated.
Wishmaker: Gohan
1. Reveal the source of the undead problem.

"Majin Buu"
When?: After the defeat of Majin Buu.
Wishmaker?: Unknown
Created?: Three-Star Dragon
1. Erase everyone (save our central cast)'s memories of the Buu saga events.

Movie 13: Hildegarn
When?: After the defeat of Majin Buu.
Wishmaker: Son Gohan
1. Open the sealed music box.
(The second wish is never elaborated on, but by the end of the movie, they mention that they'll revive everyone who's been killed, so...)

DBGT: Episode 64
When?: After the defeat of One-Star Dragon.
Wishmaker?: Son Goku
1. Revive everyone killed as a result of villains emerging from Hell/the actions of the Evil Dragons.

Namekian Dragon Balls

Seen in:
Dragon Ball Z

Dragon:
Porunga... aka "The God of Dreams" (Larger Chinese Dragon)

Appearance:
Orange balls with red stars?

Size:
Largest of the balls; much bigger than Earth's.

Creator/Maintainer:
Original set since the 'great cataclysm' (referred to by Dende in DB 260) was created/was maintained by the current Great Elder of Namek; Second set created/maintained by Muuri (Proven by DB 327? 328?)*
.
Restrictions up to Buu saga (presumably):
You have only three wishes. (Stated by Porunga in DB 292)
You can only wish back one person per wish. (Stated by Porunga in DB 292)
The wishmaker must speak in Namekian. (Stated by Dende in DB 292)
If the creator of the Dragon Balls dies or ceases to exist, then the Dragon Balls themselves cease to exist. (Proven by the death of the Namekian Guru, aka Saichôrô-sama, and thereafter stated by Dende, in DB 294)
If the creator of the Dragon Balls is revived, then the Dragon Balls will exist once more. (Stated by Kaio-sama in DB 321)
The maintaining of the Dragon Balls can be passed on from one being to another (Proven by Saichôrô-sama's passing the DB maintenance onto Muuri in DB 327? 328?)

Restrictions after Muuri becomes DB maintainer
You can revive however many beings you want. (Stated by Muuri where...?)*
Other restrictions remain the same, or can be presumed to remain the same.

Wishes used:
When?: After Ginyu's defeat, and Dende returns from the Elder Namekian.
Wishmaker?: Dende
1. Revive Piccolo.
2. Transport Piccolo to Planet Namek.
3. (The third wish was never made, due to the Elder Namekian dying before it could be made.)

When?: After everyone is revived by Mr. Popo's wish to bring back everyone killed by Freeza and Freeza's soldiers..
Wishmaker?: Dende
(As the Elder Namekian was revived, the third wish was possible.)
3. Transport everyone on Planet Namek, except for Son Goku and Freeza, to Planet Earth.

When?: As Goku and Majin Buu are fighting on Kaioshin-kai, and after Dende, Kaiobitoshin, and Elder Kaioushin go to Namek.
1. Recreate Planet Earth.
2. Revive all those who were killed by Majin Buu, save the evil ones.
3. Revitalize all of Son Goku's energy.

DBGT: Episode 39
When?: After Bebi's defeat, the movement of the Earth's population, and the explosion of Earth.
1. Recreate Planet Earth.
(The other two wishes are never elaborated on!)

Blackstar Dragon Balls

Seen in:
Dragon Ball GT

Dragon:
Original Shenlong (Huge Red Chinese Dragon)

Creator/Maintainer:
Originally created by Piccolo before he split into good/evil halves.

Restrictions for the entirety of their existence:
You can make one wish. (Stated by Original Shenlong in DBGT Episode 1)
If you make one wish with these Dragon Balls, the planet that the wish is made on will explode in one year. (Stated by Kaio-sama in DBGT Episode 1)
If the creator of these Dragon Balls dies or ceases to exist, then the Black Star balls will also cease to exist. (Stated by Piccolo in DBGT Episode 39)

Wishes used:
When?: After Pilaf reaches God's Sanctuary.
Wishmaker?: Pilaf
1. Return Son Goku to a child state.

When?: After Bebi gains control of the entire planet, and the BS DBs are within his grasp.
Wishmaker?: Bebi
1. Recreate Planet Plant