Here's some of the music and groups I like to listen to.

ApologetiX - A Christian Parody Band (think Christian Weird Al), if you sign up on their website, you can download some free (complete) songs on their site.
DC Talk
FFH - (Free For Him) Music Clips, info, ect.
Michael W. Smith - also known as Smitty (personally, I prefer "Michael W. Smith")
Newsboys
Petra - The Christian rock band. Preparing their site for their 20th Album, the site doesn't have much at the moment, but you can listen to some songs from their new album: Jekyll & Hyde
Steven Curtis Chapman
Supertones - Listen to a few complete songs, watch their videos, ect.
Switchfoot - Sound Clips, music videos, ect.

Pulse FM - A great Christian radio station, you can listen to the with the Realplayer online.
Higher Praise Music Videos - Their Music Video section has lots of Christian Music Videos from various artists.