Head to this YouTube video for an introduction to the different types of ukuleles out there, and how to choose the best size for you.
To be honest, in my opinion, I would go for either a concert or tenor 'uke. The soprano size tends to be too small for many folks' hands.
Cynthia Lin is a fantastic ukulele player based out of San Francisco and Honolulu. You can access her beginner tutorials here.
Another great channel on YouTube is Ukulele Underground. Play along with some of their videos!