And then there’s Slacker, a service which, like Pandora and Last.fm, lets you conjure up custom radio stations which riff on what you tell it about your favorite artists by creating playlists with both faves and other performers you’ll probably like. Slacker is available in free and fee-based Web versions, but it was built from the ground up to work with portable players. Earlier this year, the company released a Slacker handheld that had plenty of promise but was also kind of bulky and clunky. And then it moved quickly to replace that first version with an improved model: the Slacker G2, which is available from Slacker’s site and Best Buy. I’ve been playing with it and really enjoying having personalized radio I can stick in my pocket. But while the Slacker service is a kick and this second-generation hardware is more polished than its predecessor, the device still feels like it’s a good fit for dedicated radio fans more than for music aficionados of all types.