Hi Teri,
Can't call myself an expert in this area since dd is only 7 months old, but from many of the posts I have seen, the transition to move towards 1 nap can start as early as 10 months old and kind of go back and forth for a couple of months until they finally are down to 1. I don't want to give you any wrong advice, having just read posts and not experiencing the transtion first hand, so I am going to alert Meg's Mom of your post. She recently went through the transition and had awesome advice. I think she might have posted some information at the top of the forum as well. She is off duty today but will see if she can lead you in the right direction tomorrow.
Thanks!