I just came across Upcoming.org, which is "a collaborative event calendar, completely driven by people like you. Enter in the events you're attending, comment on events entered by others, and syndicate event listings to your own weblog. As Upcoming.org learns more about the events you enjoy, it will suggest new events you never would have heard about."
I don't know about the learning side of it, but one thing that's definitely of relevance to us is that they offer RSS feeds of calendar events for different cities. Here's their page about London:
http://upcoming.org/metro/uk/london/london/
I think if I can hack together some kind of aggregator plugin, this could be a great thing to include with the guides to provide extra depth (and an incentive to keep coming back).