protein-potein interaction prediction software - where to download? (May/16/2009 )

I'm studying the interaction between two proteins. I've heard there are softwares that can predict such interactions. does anybody know about this?

Try here

wow...thanks.
i just don't know which one to chose!

Do you know how many aa's need to be identical to say that two peptides or proteins are similar?

I am using SIM alignment tool at ExPASy website now. some times I get 5 similar residues but the score does not go higher than 30.0-35.0. is this good? the identity is usually around 70% for me.