IK Multimedia's MODO Drums has a free version. I've also noticed that after isntalling AIR Music / InMusic's free channel strip they've just given away, they now seem to own BFD drums and there's a lite version for free from them too. If you're on a Mac, then Logic's Session Drummer is useable - I guess GarageBand would offer a drum option too, but I havent used that app for ages. I do have EZDrummer 2 & 3, they are, as mentioned, paid options but very, very good. You'll hear a mixture of MODO and Logic Drums on pretty much all of my review videos. I improvise everytihing (badly ha ha) so drum loops are really useful! EZD hasn't featured much, I should get it back on track!