If you want to try out some drum beats from scratch but don’t have any software, there are some web pages that allow you to make some beats of your own.  Granted you’ll only be able to do drums - not bass, string pads, chords, etc, just drums.  You’ll also need to know how to work with a drum grid for most of them.  If you don’t know what beat to put a bass drum on, or snare you can take a look at how to make drum beats from scratch.  There aren’t too many out there but here’s what I could find. So here we go.

Groovelab - browser based, sounds ok, but you don’t get to preview beats.  You have to make your beat then it gets compiled so that you can hear it.  You can then download it, which isn’t always possible with a lot of the programs. 

aMLabratory - A Roland 909 emulator, basically has a 909 interface.  There isn’t any easy way to get the audio on your machine, so I don’t know how useful it would be.

Drum virtual machine online game.  Don’t bother, basically a lame attempt to get you to click on one of their ads with a crappy flash game.

Monkey Machine - The drum samples sound really good, it’s set up with the standard drum grid, again no downloading of beats.