Debuggex: A visual regex debugger 
This is the best RegEx web-site that I have seen. It is actually quite far ahead of everyone else.<p>Unfortunately if you don't "understand" RegEx it won't help much. It is more for people who already have it down.<p>For me I am still stuck in copy/paste land. I could never get my head around the "logic" of RegEx, it just seems completely random and arbitrary.<p>Plus they re-use the same characters but have multiple meanings (e.g. ^ for NOT and for START).