XSS is one of the ones really easy to do manually, i mean all it requires is a <script>alert('xss')</script> but i know acunetix has a pretty refined XSS module, but search packetstorm theres loads of xss tools and also firefox addons, but i dont personally use them.

I think theirs a firefox plugin called XSSme which has good reviews, you may wanna try that if you cant do it manually.