A note to add is that, from 18th December, Left 4 Dead on Steam is updated to version 1.0.1.7.
The cracked servers all run v1.0.1.6, so legit copies can no longer play on cracked servers
I'm trying to find a work around, but I'm starting to join the "i hate steam cos it won't le me be a pirate, too" camp.
Hopefully, before too long, there will be a patch for cracked games to go up to v1.0.1.7
The server list above is still valid for working patched copies on earlier versions of the game (v1013-6 on correct server protocols).