I was pleasantly surprised the first time I found free sounds on the main ableton site; I didn't know a software company would also give away extra things to use with their program. Very cool. There's actually a ton of stuff on ableton.com so remember to take a look (after you read this post and LOVE IT of course.)
"DM-307A: Heavyocity brings its flagship collection of analog and organic drum sounds to Live: a carefully processed, production-ready batch of live percussion, drum machines and modular synth drums."
Take a listen from their soundcloud playlist. I loaded these up and played around a little bit last night. The soundscapes are kind of dark for my tastes but the single hits and drum sounds magnetized my brain right away and I made a track with them instead of writing this. Now it's tomorrow again.
Anyway, they're really well produced, using analog source gear and some boutique hardware in the signal chain, and you can DOWNLOAD IT HERE.
Update: here's the Ableton.com free downloads page, which they are updating regularly with M4L devices and other surprises.