there are thousands. Most require a username and password to access, unlike suprnova. Supernova is a leechin g and run place. There are many good sites that when you become a part of them, you find people who actually share. I could list you off about 20 that i use, but the best thing to do is just google for them.
I think at one time, maybe before a crash here, someone started a list of sites.
One i will promote is isohunt.com. They are doing some neat stuff over there with indexing multiple sites, including suckrnova.org.