I've downloaded and installed mplayer, angry birds, kmplayer, canola2, and none have any sound.

Games that were already installed on my n900 have sound though like mahjong, blocks, marbles.

Media player works.

Any ideas what's happening or what i'm missing?

I'm assuming you've checked volume, silent mode, etc.

Try a reboot. It usually fixes things like this.

If not, Canola2 may be the culprit.

If you're not a power-user or developer, by all means stay out of Maemo Extras Development.

I've tried Canola2 before on the N900, and it's obviously not ready yet.

Try bumping this thread every once and a while with more info, because past quick-fixes, I'm not an expert.