EXS 24 Logic Sampler Users Group

Here are a couple for starters:

http://kontakt.daw-mac.com/drums.html

(someone created an EXS file for this one but I can't find the link---I'll 
provide it if nobody puts the link up)



http://www.natural-studio.co.uk/nskit_download.htm



And there's a page with lots of freebies at the EXS Yahoo files section:

http://groups.yahoo.com/group/exs-users/links/