Since switching from an iPod to my Android phone as my main portable music device, I've noticed that most Android music apps don't have rating capability and if they do, the ratings don't sync to desktop software.

I use RTM to store my ratings to rate on my desktop later (foobar2000).

To do this, I create a task with the album name as the title and tag it "rate". After a song finishes, I add its rating (one per line) in a note attached to the task.

You can also do this with any playlist. Just use the playlist name as the task title.