You can, but your blood type isn't universal. I suggest you still donate or maybe donate red blood cells.
Yours isnt universal either....Everyone should donate blood, if medically able to do so, all types are wanted. Only a very small percentage (I think 6%, google it) have the univeral blood type (Type O Negative) and the blood centers are not picky about your blood type-they want it all.
Dont use a donation center as a HIV test, not only is that tasteless and shitty but sometimes things slip by and if you are infected you could screw someone over really good.
Donating FTW
EDIT: BTW, if any of you are type O negative, you should donate like a MF. Its good karma anyway-you can donate to everybody BUT only type O negative can donate to you. So if youre squeamish, suck it the fuck up.