There are various online hangouts of XLers...

There's email based groups like Grax and PJAXI

A lot of XLers have profiles on Ryze, check Madhukar's page for a comprehensive listing of XLers there.

Quite a lot are on Linkedin. In fact Kim ensured that we have a XL Alumni group on Linkedin too.

And there are lots of XLers on Orkut, the social networking site. Some XL-related communities on Orkut are XLRI, XLRI (smaller group), Fraxers, MadFaxi, VLAXI, PFAXI. The last three are Prof fans associations !