Wait, wait... A few hours ago I submitted a link about Sponty and how they can compete with Foursquare. (http://news.ycombinator.com/item?id=969221).

It's kind funny how the techcrunch article gets instantly lots of votes, and link to random blogger gets ignored.

Anyway, Sponty also offers a social calendar, where you can broadcast your intentions, and also have feeds for different events.