First of all, what kind of pattern are you looking for (eg. sweaters, hats, bags, etc)?
I just did a search for "Hello Kitty" on Ravelry.com and came up with lots of different patterns ... here's the link to what I found:
http://www.ravelry.com/patterns/sear...=Hello%20Kitty
If you're not already a Ravelry member, you'll have to sign up to view the patterns ... it's free to sign up, and the website is really great for all kinds of things!