I used the Napster $9.99/month service for over year and liked it because I could download whatever songs I wanted, play Radio Stations, etc. I just recently found Real Player's Rhapsody which has the same service for $9.99/month, but they have more music than Napster and even iTunes (I have checked, trust me). You can use Rhapsody with almost any MP3 player (including the iPod), and all my purchased tracks from Napster I easily imported to Rhapsody so that I can still burn them whenever I want. Also, if you have the $9.99/month service, tracks only cost $.89 a piece (compared to Napster's $.99) and I don't know if it's an ongoing thing or limited time, but since I've been a member (several weeks) all albums sale for $7.99.
