What should I be looking at in the used lens market for upgrading my 18-55 kit lens? My budget is about $500 or less (or less would be real nice). I'd use this as an all-around lens. Being able to shoot indoors without a flash would be a real plus, so I'm wondering if one of the 2.8's is within my grasp. I'm open to manufactures other than Canon as well.
Thanks in advance for your expert opinions.

