I picked up the Canon EF 50mm f/1.8 II Camera Lens off Amazon.com a week or so ago and last night I did some testing to see how many stars I could pull in. I played with Exposure times to see how long I could keep the shutter open before getting star streaks. I found its a fine line, but 15 seconds is good to go, while 30 seconds is just too long.
The first picture here is reduced in size and the stars have some movement (longer exposure).
The second picture of just the stars is a pretty big image (I left it the origonal size of 3888 x 2592) but shows that keeping the shutter open for only around 15 seconds pulls in a ton of stars.