I am bored but don’t want to spend money or download anything.
Trackmania Nations Forever
Spiral Knights is up to date and really fun, has upgrades and stuff.
If you're looking for, more or less, browser based games, then I'd suggest http://www.teagames.com. They have a variety of games that are pretty impressive. Not all of there games are golden gems, but there are some in there for sure!
APB Reloaded (very fun MMORPG): http://gamersfirst.com/apb
Battlefield Play4Free (FPS): http://battlefield.play4free.com/
AVA (FPS): http://ava.ijji.com/
If you're into MMORPG games Runecape is worth a look. It's not the best, but for being free it's pretty good. There's currently a lot of bots and scammers, but still not bad overall.
check out the articles in this list for a ton of free online games!