I've been repairing my own small dings, pits, cracks and bullseyes for the last 3 years. It's not tough to do and I find it helpful to repair them right away before the cracking starts (or starts spreading). By the time you get the car to a repair shop, the crack has often spread beyond repair.
I use the following product:
http://www.amazon.com/Permatex-16067.../dp/B000HBI9XW
It not only works for bullseye damage, but I keep the syringe of resin around and repair knicks and cracks as they occur. You just put a few drops over the damaged area, place a thin piece of clear plastic over top of it and leave it overnight to soak into the damaged area...including cracks. Next day, expose the area to bright sunlight for an hour which UV cures it. You then scrape the surficial cured product off the windshield with a razor. Damaged areas become almost invisible, and I've never had a crack spread once it's been repaired.