Mark Diodati points out this interesting open source SPML gateway. There is an accompanying blog by Jerry Waldorf of Sun that has a lot of background on the project and presents some interesting concepts of things that you could do with an SPML gateway.
This is exactly the kinds of stuff I had hoped to see happen when I started working on SPML. Working at Access360 it was frustrating to see so much time and effort spent writing connectors to all the disparate systems that needed to be provisioned. If only project keychain had existed back then.
Great stuff if you are interested in provisioning.