Nice library. I wrote a small jQuery form validation library called Chackmate [1] for a project I was recently working on. I think the reason that so many end up writing their own validation library, despite that fact that there are so many already out there, is because everyone wants to handle the validation a little differently. Form validation is something where it's arguably more effective in the long run to roll-your-own rather than learn someone else's code.

[1] https://github.com/reidHoruff/Checkmate