I'm assuming this is BPM, if you want something a bit harder. IMO needs an option for ambient/downtempo stuff I personally find it hard to get stuff done to dance music.
You might like somafm.com, they have some great channels including beat blender, among others. Ad free too.
Di.fm is also good for the same reason. I find I listen to Soma more though because of Groove Salad.
I totally forgot about groove salad. I'll check out di.fm .. for now I'm liking getworkdonemusic.com a lot.
If you're looking for ambient/slower tracks I would check out Ghostly Discovery: http://ghostly.com/discovery/play/ cool interface and great music.
I love this! The only missing is a mini-player theme, like this Chrome app mock-up: https://dl.dropbox.com/u/9196433/news.ycombinator.com/ghostl... Clicking on the album cover would pop-up all of the album specific stuff, clicking on the (i) would give you all the "static" stuff.