There are two sites that keep up with the game.

http://www.sgt-dan.com/ and www.megagames.com

Usually the patching companies (Paradox = www.paradogs.com, Kalisto etc) distribute "silently". For example you won't find a Kalisto web site (the cracking company that is).

Patches come out irregularly. Search the web on PS2 Patches and you'll see a few more names pop up.

You need to know why you are patching, of course. For example, it isn't necessary to patch a PAL game that doesnt require a protection fix if your target is a PAL PS2, or if you have an NTSC PS2 and PAL TV with a NTSC to PAL convertor