Tedi - Tom gave some very good advice.
Read through the posts on
Photoattorney.com Carolyn gives great advice and will work for you as well. She gives some great advice on the first steps you should take, do yourself a favor and read through her blog.
I have met Carolyn and she is a no-nonsense person that aggressively defends her clients and photographers.
PPA offers free consultation with an attorney in cases of copyright violation. They do not cover the entire cost of a case if it works out that way.
Keep in mind that many folks lose more money than they will make if they go to court in copyright violation cases. I know of one that the attorneys fees more than tripled the award amount.
I dealt with a copyright violation a couple of years ago, I followed Carolyn's advice, wrote a letter, and they settled and I got paid. The key thing to remember, try not to get emotional about the case, that will only make things go poorly. Also be realistic about the value of your image, understand the usage and how that determines the value.
Good luck and let us know how everything comes out.
Scott