Short term gains are taxed as ordinary income so whatever bracket you are in they are taxed at that rate. So it could be 10, 15, 25, 28, 33 or as high as 35% plus state tax.
Long term gains are taxed at 15%, unless you are in AMT. Also long term gains when you are in the 10 or 15% bracket are taxed at 0% for tax years 2008 to 2010.
Look for long term capital rates to go to atleast 20% in 2011 and after.