There are some good Dance/upbeat stations around on the net these days.
Non-Stop Play, finally updated and sounding fresh and very tight. It's been around for 11 years amazingly! As part of their relaunch, they now have 2 stations...Non-stop play mainstream, which oddly includes some indie rock....not too sure about that myself! But they have non-stop play pure dance too, which does what it says on the tin. Listening to Pure dance myself.
http://www.nonstopplay.com/ (although you have to use the popup player to find it, quite hidden for some reason!)
www.crucialradio.net is pretty fresh as well, they have Dave Pearce on now - guessing it's the same show which is available on FM, but a pretty big coup for a net radio outfit I think. They have some impressive names at the weekends all being told, after having a look through their schedule. Some great sounding music on their playlists during the day too, and it's always kept very fresh and up to date.
Also one mentioned above,
PowerON EDM is a good station - a proper anthem sounding playlist. Their website is great (although not keen on it playing automatically on visiting), easy to use and quite stylish - I quite like their promotional slogans and all in all, quite a good outfit. Their sung imaging is a bit different, but annoyingly catchy! (so i guess it works!)
Rapture Radio is another good one, pretty much non-stop jukebox dance....but full of great classics and the latest dance from today, a really good listen and you can hear the work that goes into it - really slickly produced - and if you're nostalgic like me, you'll get flash backs when you hear the imaging as it's just the audio of what was in use on RaptureTV all those years ago!