Another site that I'm hearing about is Pandora, created by The Music Genome Project. It asks you for a song or artist you like, and based on the Music Genome Project's vast analysis of song characteristics, it creates a personalized radio station. You can tell Pandora whether you like or don't like the songs Pandora is choosing for you, and it will further customize your song list.
I created a new station based on the punk band Rancid and ended up with some punky new finds.
There is a sea of blogs out there, and if you can find a blogger who shares your taste in music, then you're golden.
Anthony Gordon, the artist relations specialist for Digidesign (which makes Pro Tools audio gear), gave me his picks. Hype Machine is less a blog than a best-of collection of other blogs--which is useful in and of itself. Puritan Blister has an eclectic collection of mash-ups (two or more songs merged into one) and "tons of cover versions of songs that will never be officially released," says Gordon. Death Cab for Cutie's cover of Avril Lavigne's "Complicated" is one of those. By the way, if you like mash-ups, visit Party Ben.
Many of the sites mentioned here, such as KCRW and The Hype Machine, provide podcasts and RSS feeds. One recommendation: the Next Big Hit podcast.
I hope we all make the effort to seek out new musical genres that push the boundaries of what we're comfortable with--and buy those albums online. The more we do, the more search engines will spit back music recommendations across genres, reading something like: "Customers who bought this item also bought ... something totally different."