Finally at the lowest $99 level. Hadn't seen it posted here, figure most people have heard of it elsewhere, but the first GB had some amazing sounding drums in it, so it's worth mentioning here too. It's actually a group buy, but already reached its lowest price; from here on, it's just how much extra you'll get over what's already in it. You can join here: http://www.esoundz.com/details.php?ProductID=4181
If you need real drum sounds, this is a great deal to get in on. I was in the first GB, and some of the drum kits are larger than 1GB, and sound incredibly realistic (and I'm only playing through a nanopad right now). This one includes ~25 drum kits in total (so far), about 17gb total, 1000 midi grooves from Groove Monkey and Sonic Reality, + a bunch of impulse responses from famous studios to help you get the 'sound' of that studio on your own tracks. The kits are played in their own Impulse Player, which in turn becomes a part of Kontakt (either the free kontakt player, or a full kontakt version).
They've already added some extras... you get Impulse Player for free plus an extra multitrack kit, or if you already have impulse player you get 2 MT kits from a selection of 8. There will be more as the number joining grows.
To bring this back on topic a little bit for here... I also have Session Drums, and I got that Steven Slate audiomidi deal too. So how do they compare against each other? The slate drums are great for rock but really I think they are the least realistic. Session Drums, though it's pretty old now, actually holds up very well, with good variety, but I'd have to give the edge for sound to the sonic reality stuff. After playing with a few other drum libraries (this one, Slate, Addictive) I'm actually impressed with how good this ableton add-in sounds, though it doesn't quite have the range of the USD group buy. The first USD group buy had Ocean Way Drums and Drum Masters, and has some really lively and raw-sounding drums, with a wide variety.
I originally got into the first one, because I kept hearing that ableton built-in instruments were somewhat limited and I wanted to see what a 'real' drum library sounded like. And, at the time, it was pretty much the cheapest way to get anything real. Now there a couple reasonable choices (ezdrummer and slate have both appeared recently <$100), but this is still a much better deal IMHO. I just got into this really to learn more about programming drums... i've never really 'gotten' drums well. Now I'm excited enough about drums I want to get a real e-kit
if you need a reference when you sign up, you can use my nick: chroma. if you use a reference, both you and the person get 5 epointz, so it's worth putting someone down.