Regular Expressions is a not for mortals like me. I have about 3 yrs experience using these in various projects in my life. But, still kicks the heck out of me. I usually fall back to various resources when I'm lost. Off the many survivors on the web to service questions related to this space, "Regular-Expressions.info" site is probably No.1 on my look up sites. They have various expressions examples that you can freely use in your code. Plus, the examples come with full description to what role each of the params play in the expression. Offlate, I've been using this site a lot for my photo blogging engine, "f/stop".
Hope you find this site equally useful as I did.
ciaoNagi