Last.FM employees have their own secret hideout. It's called the Playground, and it's the place where they showcase new cool applications and weekend projects they've been working on. The really cool thing about it, though, is that it's not really secret anymore.
The public version of Last.FM Playground brings three applications: multi tag search, search for variations on an artist's name, as well as a weekly chart of tracks most frequently used in users' top 10 lists. Admittedly, it's not as flashy as Digg Labs, but the official announcement mentions "complex visualizations," so we can hope for cool ajaxy goodness sometime in the future.
Currently active projects depend on you, the user; if user feedback is good, they live; if not, they'll be removed when they reach an expiry date.