http://www.google.com/search?q=%22windows+rootkit%22 184 results windows rootkits.
http://www.google.com/search?q=%22linux+rootkit%22 548 results linux rootkits
http://www.google.com/search?q=t0rn+rootkit 928 results t0rn rootkit

Google is always your friend. Have fun parsing that much information.

http://www.sans.org/y2k/t0rn.htm Analsyis of t0rn rootkit (got link from google...)