7Timer has to be the bees knees. It seems to be very accurate, and has a dedicated Astro Panel:
http://7timer.y234.cn/index.php?prod...zshift=0&site=
There is also an associated iPad app that I use (all in Chinese, but easy enough to work out) but I can't see what it's called in English to be able to help you look it up. I'm sure that someone else here will remember if you need to find out.
Better still, Simon here coded up his own excellent app called Sky Harbinger that uses 7Timer data, and that's available for free (and in English) in the iTunes store.
Dean