I have used Macast (www.macast.com) for several years and love it. I currently have over 26 hours of music on it. I don't know whether or not there is a limit. It costs about $20, but is well worth it. The e-mail support is very good.

It has a nice features, like a place to put data on each selection (artist, song, album, date, etc.) plus a place to add song lyrics, or whatever else you'd like to add.