I've just been playing around with a cunning thing called FoaF. The idea is that you create rdf files which contain data about yourself, and also links to other people you know. FoaF stands for Friend of a Friend - so if there are enough people with FoaF files then you can see who knows who and stuff.
Here is my FoaF file.
Suppose that doesn't make much sense... well FoaF Explorer. So far I've only linked to Antony, but I'm sure that'll there will be some readers out there who will want to make a file for themselves - it's dead easy!