I was looking to make a small event registration app but I thought i would check to see if there were any already floating around to check out, I did a quick google search but didnt really find anything...
eventwax.com (in rails, too!) upcoming.org meetup.com
Nothing open source that I know of...
There’s also the very lovely pingg.com (again not open source).
thanks, I found a lot of useful info at eventwax, shame its not open
source 