We just started this week (7 months old) and have the Healthy Times Maple Teething Biscuits. My DS loves them and they have yet to break, but he doesn't have any teeth yet.
Mummums are great, not for teething but pacifying while you make food, and you will feel more comfy once you see your baby will gum the heck out of them. We use gerber biscuits for teething. We started at about 6 1/2 months and he has yet to bite a chunk even with teeth. We tried earths best and I had to rake a chunk out of his mouth, it broke right away...
Re: Poll: When did you start teething biscuits?