A highly comprehensive collection of protein interactions databases, predictors as well as web tools can be found here!
Notably, PIBASE is a collection of all protein structural interfaces extracted from the Protein Data Bank and PISA structure databases. Both chain-chain and domain-domain (SCOP and CATH definitions) interfaces are detected. A series of properties are then computed for each domain, interface, and complex.
You can also test several interface calculators, such as ProtinDB and PIC.