Finally received my invite to the pinwheel social networking site tonight. First heard about it on the Triangulation Show, and was intrigued. Signed up that night and a few days later got the email invitation to join up. Basically you have a map of the world at your disposal, down to street level (your detail may vary, as usual with google maps, and openstreetmap) and you can leave notes and images at those locations. The notes will, it seems, allow hyperlinks so you could include a link to a URL of your choice. Images can be uploaded from your machine (or from anywhere - just use your machine's file browser as presented and paste in a URL - it doesn't mind) and are then associated with that locaton.
You can also tag your notes with, um, tags. They become 'hot' so you can click on them and connect to other folk who have used the same tag. By tagging with genealogy I've found somebody who had various 17th century ancestors beheaded, stabbed in the back etc - it's all good.
Notes may be public, private, personal - with corresponding visibilities on the world map. Early days yet, not huge numbers of people, but by the time I arrived my home town had already been pinned (but only half a dozen times at the time of writing).
I wonder if it will take off?