Stargreen VCALENDAR FeedsStargreen, a UK booking agent, publish RSS feeds for their listings, but no ical/vcalendar feeds. Here are .ics files made from those feeds. I've tested them with Apple iCal, phpicalendar, WinDates, and eventSherpa, and they seem to be fine. What's On for the UK, in your iCal!
The files are collected from Stargreen every 6 hours or so, so if you want to subscribe to these calendars in your calendar app, then once a day is often enough.
UPDATE August 2009: Fixed a problem with the date parsing. Looks like all but the 'events' feed are basically dead.