A lot of people have recommended Cyndi's List, but this has not been very useful to me. It seems to just have links to random sparse facts.
I have traced my Polish family back to the 1700s and have a lot of useful info on how to do it. The best resource was the local Family History Center run by the Mormons. You must find the villages or towns where your family came from first, and then you might have to search around villages near there. Google Maps can help you find nearby towns.
The birth, marriage and death registers available through the Mormon Family History centers are very difficult to read in some cases. They are available on microfilm. For my family, which was Catholic, they are mostly in Latin. There is some Polish every once in a while. Mostly I have looked at church records, which were basically the same as civil records in the 19th century. Of course, back then, Poland was administratively part of Austria, Russia, Germany, Prussia, etc.
A couple of really, really good books are "Polish Roots" by Rosemary A. Chorzempa, and "A Translation Guide to 19th-Century Polish-Language Civil-Registration Documents", by Judith A. Frazin. The first one is readily available, probably on Amazon (or through Ancestry.com), and the second one is only easily available through the Polish Genealogical Society of America (at pgsa.org).