Daizenshuu 7 has two pages on the races of DragonBall, and it starts out listing the various races in the series. The main ones of course are the Earthlings, Saiyans, and Namekians.
Then there are the Nikochan-Seijin and Okakaume-Seijin who live in Penguin Village. “Nikochan-Seijin” is the race of King Nikocan from Dr. Slump, who appears in DragonBall very briefly during when Goku goes to Penguin Village. He's short, green, has antennae, and his forehead resembles a butt (and even farts). Okakaume-Seijin is Suppaman's race. In Japanese, sei means “planet” (and star, and pretty much any other shiny object in the sky), and is added on to the names of planets, while jin means “person”, as you probably know. So X-Seijin basically means “person/people of Planet X”, and it's the generic formula for alien races.
After the main races and the Dr. Slump aliens, it lists the races from the anime, both filler and movies:
That's quite a list. You probably know what many of those are, but I bet there are quite a few you've never heard of. To tell the truth, that list has been driving me crazy for awhile, since I've been trying to figure out some of the races. Part of the problem is that a lot of those movie races were only named in background information that didn't make it into the movie. For instance, before DBZ movie 5 premiered, there was an issue of Weekly Jump that provided lots of background information on Coola's henchmen, including what planets they were from. Of course none of this got mentioned in the movie.Tsufuru-jin, Brench-Seijin, Beppa-Seijin, Zalt-Seijin, Makyo-Seijin, Litt-Seijin, Shirts-Seijin, Tabbu-Seijin, Kanassa-Seijin, Meat-Seijin, Kuhn-Seijin, Ahter-Seijin, Aria-Seijin, Konattsu-Seijin, Shamo-Seijin, Beanz-Jin, Ikonda-Seijin, and the Race of Hera.
The really annoying thing is that even the daizenshuu don't really record this background information in an encyclopedic way, they just make offhand references to random bits of it. So going back to the Coola henchmen, that issue of Weekly Jump said Sauzer was from Planet Brench. Daizenshuu 7's bio for him doesn't mention this at all, but then “Brench-Seijin” gets listed as a race in the race section, and the section on languages mentions that he is the “genius of Planet Brench who knows 7,000 languages”. So you end up with that race list above, where some of the races are never explained or even mentioned in any other part of Daizenshuu 7. Kind of annoying...
To find out what these races are, I've been searching around the Japanese Wikipedia pages for DragonBall stuff, and other Japanese websites. So here's my annotations to that race list, with explanations for both those super-obscure races and the more familiar ones.
Tsufuru-jin: These are of course the original inhabitants of Planet Vegeta (which they called Planet Plant), who the Saiyans wiped out. Though they only appear in the anime, they were thought up and designed by Toriyama. Their name is a pun on fruits (furutsu).
Brench-Seijin, Beppa-Seijin, Zalt-Seijin: These are the races of Coola's three henchmen from DBZ move 5. Sauzer is from Planet Brench (a pun on french dressing, just as Sauzer's name comes from thousand island dressing), Dore is from Planet Beppa (derived from pepper), and Neiz is from Planet Zalt (a pun on "salt", as Chibi Mystic Gohan points out). Sauzer is distinguished as being the “genius of Planet Brench” and knowing 7,000 languages. Planet Beppa is a lava-covered world, while Planet Zalt is covered completely in water.
Makyo-Seijin: Garlic Jr.'s race, who come from Planet Makyo. The dub calls Planet Makyo "Makyo Star" (I mentioned earlier that sei can be both "planet" and "star"), but in this context it's clear that Makyo is a planet.
Litt-Seijin: This is the small race who Gohan and Kuririn's battle armor they wore on Planet Namek was designed for. Their name is most likely a pun on “little”. In the Viz manga, they are called “the people of Planet Lilliput”. In the manga they are only mentioned by Vegeta and never actually appear, but in the Garlic Jr. filler arc, Vegeta is shown slaughtering them. The anime gives them a birdlike appearance.
Shirts-Seijin: The inhabitants of Planet Shirts, who Vegeta, Nappa, and Raditz wipe out in three days, as shown in a filler scene. They look basically just like humans.
Tabbu-Seijin: The only one I haven't been able to figure out. Though I think the name might be a pun on buta, Japanese for "pig".
Kanassa-Seijin: The people Barduck and his crew wipe out in the Barduck special. Their name is a pun on sakana, Japanese for “fish”, which they resemble. The only one of them given a name is Tooro, who isn't called by name in the special itself, but is listed in the credits.
Meat-Seijin: The other race Barduck's crew wipe out in the special, before Dodoria and his men kill them all.
Kuhn-Seijin: The inhabitants of Planet Kuhn, one of the planets from Plan to Exterminate the Saiyans. They resemble dogs, which is where they get their name from (“ku~n” being the cry of a dog). Some of them can predict the future. They are harassed by the space pirates from Planet Ater. Because of this, the town on Planet Kuhn is named Pirates.
Ater-Seijin: The inhabitants of Planet Ater, the other planet from Plan to Exterminate the Saiyans. Most of the planet is water (hence the name), and they live underwater. Some of them are space pirates. The town on their planet is named Aqua, for obvious reasons.
Aria-Seijin: The insectoid race that Vegeta and Nappa destroy in a filler episode. I think their name might be from ari, Japanese for “ant”, though they look more like grasshoppers than ants. Maybe they're just all opera fans.
Konattsu-Seijin: Tapion and Minoshia's race, from DBZ movie 13. Planet Konattsu is in the southern galaxy, and it's name is a pun on “coconuts”.
Shamo-Seijin: The small, mohawk-sporting race that Paragus enslaved in DBZ movie 8. Planet Shamo itself is destroyed by Broli midway through the movie. Goku rescues them from the destruction of New Planet Vegeta. Somewhat confusingly, one of them is actually named "Shamo" (the Vegeta of his race, perhaps?).
Beanz-Jin: The race of Turles' two henchmen Rezun and Rakasei, from DBZ movie 3. Their race is actually extinct, and Turles revived them from a petrified state using extract from the Shinseiju fruit. Note that they're “Beanz-jin” and not “Beanz-Seijin”, so it's unclear what the name of their home planet was. Anyway, the name is an obvious pun on “beans”.
Ikonda-Seijin: The race of Kakao, the big red cyborg from DBZ movie 3. I think the name might be a pun on daikon, Japanese radish.
Race of Hera (heraa ichizoku): The race of Bojack and crew, which they are the only survivors of. I don't know what it's a pun on.
Here's a bonus one, not from the list: Alpha-Seijin. They're the race of vaguely toad-like aliens who Kid Buu wipes out in the filler scene that shows Buu's origins. Their name is often mis-romanized as "Aruhua-Seijin". The name comes from Daizenshuu 10, which shows their character model sheets, though it mistakenly describes them as the inhabitents of the planet Buu wiped out while searching for Goku and Vegeta (the inhabitents of that planet were never shown).
)