Have you looked at http://www.opencores.org/ ?
Is there anything on the Philips site?

An AltaVista search for I2C+VHDL gave >800 hits, and I2C+Verilog gave >600.

Have you thought about a Triscend E5?
The FastChip development tool comes complete with an I2C SoftModule.

(Don't tell 'em that I told you, but you can export the SoftModules to VHDL...)