http://yournextfavband.com/ Found that from the last.fm profile of one of my neighbours on the site. So I plugged my username in, and it tells me...
All righty photongenic, we looked at your top 20 neighbours, and we think your next favourite band will be:
*drumroll*
Perfume
as listened to by 6 of your neighbours.
A little behind the times, aren't we?