Use a faster lens, like a 50, or 85mm f/1.4. Depending on the camera used, you can get pretty good results with fast lens/high ISO shots to avoid having to use flash. What the other answer noted about using a stabilized lens is useless for street/candid photography, what good will having the ability to shoot at 1/6 a second when your subjects may move without warning? Stabilized lenses prevent camera shake, not subject motion, and candid shots are unpredictable, so I wouldn't rely on a stabilized lens. I'd rely on a fast lens, like f/2 or faster. Look into the 50mm f/1.4, virtually every camera make has one.
