Well, I also would recommend some free ones, that I believe are worth a try.
GunBound, its free, and very much like Wormz, but its online, and you can have millions of different avatar combinations. And a good choice of items, vehicles(which you battle in), avatar items, and maps.
Gunz the Duel. Well I have not played much of this one, but some friends like it. I think its alright, its a Third Person shooter(its free), and you get Gunz, Acrobatic Skill, Grenades, Swords, etc, and try to get the most kills possible in varity of matches(Team Death Match, FFA, etc).
Mmm... I have heard good things about Americas Army.
PlaneShift may, be a good choice if you are willing to try out a Free MMORPG, it is currently in development, but it looks pretty cool, and it seems like it has huge potential.(Community seems to have a huge effect on the development of the game)
Now this is not an online game, but I think it is an awesome platformer. Its called Glace, and its pretty cool.
I also can HIGHLY recommend DUO, MONO, and DUOtris. From BinaryZoo.com. They have an online highscore system, but that is about as much internet interaction you will get. They are AWESOME Games, and are some of my FAVORITE PC Games.
Warcraft 3, has some impressive online maps which you may want to try out.
Guild Wars is another good choice. No monthly fee! MMORPG, but if you can't commit 5+ hours a week, that is fine(I know some people that play 20+ hours a week of Final Fantasly XI). It does not require a huge amount of time to commit to it. Oops it still cost 49.99... maybe it is not the best "Budget" Game.
Also NcSoft(creater/publishers of City of Heros, City of Villians, Guild Wars, Auto Assult, etc) are about to release 2 FREE MMORPG. One called Exteel(Giant customizable Robots, in cool fights with swords, gunz, missles, jet packs, etc), and Dungeon Runners(Dont know to much about this one).
I recently picked up Dungeon Seige(at Target for like $7), and I think it is pretty pretty cool, and I know it has a online multiplayer mode too.
Ive heard many good things about NeverWinter Nights, if RPGs are your thing, you can download a demo. And Ive heard there are some pretty cool servers(or what ever) you can play on.