A good place to start is the link that says PC installer - all formats on this page

http://www.groovemonkee.com/en/free-midi

That will give you the free MIDI patterns mapped for all formats. 

You may also want to check out Platinum Samples for both MIDI loops and Session Drummer Expansion Kits.

Hey I downloaded the 2 free downloads from groovemonkee - not bad at all. It sounds pretty natural. cool
 
do you have a link for the Platinum samples session drummer expansion kits?
 
Sebs

The kits are available at the Cakewalk store or directly from Platinum Samples http://www.platinumsamples.com/index.php

IF you are into really heavy stuff, SlamTraks has some really cool heavy/hard grooves. And they are inexpensive. $20 get you a pack, downloadable. They are a smaller company, if you havw a questions, takes them a few hours to respond, but I purchased their stuff, and it is pretty cool.


http://www.slamtracks.com/products-page/

Addictive drums is pretty awesome as well.