You posted in general tabletop, so are you looking for something that can be modified for different types of game systems or something for a specific genre?
Edit: this was the first search result when I typed "customizable rpg character sheets" into Google:
The Easiest Application to Play Online or IRL Role-Playing Games. Make your own Character Sheet Online, Share them, Edit them in real time, and Play with your Friends Simply
I don't see anything on the main page as to whether it is free or costs something to use after you register.
