This is something I have been looking for for a while, in the local tech community we are trying to organise all the upcoming tech events, and we have been looking for a calendar application that would support the ability to share and filter events between lots of people, being able to see who else is going to the events would be a massive plus. Currently using google calendar but it is a massive pain.
(worth mentioning at this point that its probably not something we would want to pay for)