Below are some websites that may help you with the Poland side of your genealogy search.

Archiwum Główne Akt Dawny (AGAD) – The Central Archives of Historical Records
Provides access to online registry books and other digitized parish records from the Eastern areas of Poland, now in Ukraine. Has scans for the areas of Lublin and Subcarpathian as well.

BaSIA
This database contains more than 4 million entries from all over Wielkopolska (“Greater Poland,” in modern west-central Poland) and Kuyavian-Pomeranian. With a focus on the region in the 18th to 20th centuries, this easy-to-use database contains indexes that come from state and church archives, with some links to scanned images.

FamilySearch
Has an extensive section on Polish Research, including 41 learning courses.

Genealodzy.pl
Homepage of the Polish Genealogical Society (Polskiego Towarzystwa Genealogicznego) , based in Warsaw. This site is a comprehensive resource with many databases and searchable tools.

Geneteka.Genealodzy.pl
Geneteka is a database of nearly 25 million Polish vital records that have been indexed by surname and given name, from parishes and registry offices which are grouped according to the contemporary province in Poland in which they lie. 
A detailed, 3-part, instruction guide for the site is available:

HalGal (Halychyna/Galicja)
This website provides general information on Halychyna/Eastern Galicia. This site should be the starting point for anyone researching their ancestral roots in Western Ukraine/Eastern Galicia.  Many of the pages will be useful for Polish researchers of Western Galicia, as well.  

Index of Global Newspapers
A great international index of newspapers. Go to Europe, then scroll down to Poland to see all the Polish ones that are available.

Lubgens
This site is focused on the Lublin area and has a large index of the church books as well as some scans.

Metryki.GenBaza.pl
A website dedicated to scans and photos of Polish vital records as well as civil records. The information is from the archives located in many Polish cities.

Metryki.Genealodzy.pl (Skanoteka – Metryki)
A database of the Polish Genealogical Society of Poland which has scans from different Diocesan and State Archives. This site requires registration, which is free. 

My Pomerania
A free database of Polish and German collections from the Pomerania area.

National Archives in Krakow
An online collection of things like census, church books, and civil registers

Poland GenWeb
This is a website where you click on a Voivodeship on a map and it takes you directly to resources related to that area.

Polish Citizenship by Descent
Intended to help individuals of Polish descent reconnect with their heritage and strengthen their ties to Poland. It outlines the process for applying for dual citizenship with Poland, and also has great links to topics on Polish genealogy, culture and history.

Polish Roots
Has extensive information on Polish history, culture and genealogy, and maps.

PomGenBase (PTG)
The Pomeranian Genealogical Association provides online indexes to birth, marriage and death records for the Pomeranian and Kashubia area.

Poznan Project
The Poznan Project is an index of marriages that took place in the 1800s in the Prussian province of Poznan. This collection covers parts of Greater Poland and Kuyavian-Pomeranian.

Pra.in.ua Project
This is the largest database of Ukrainian residents born between 1650 and 1920. Western Ukraine was previously part of Poland and the Galician partition. The opening page outlines (in English) information that is available through the site. 

Projekt Podlasie
Has indexes of record books from churches, courts and notary offices from Podlasie and Masovia. 

Polish Origins
Article about how to obtain birth, marriage or death records from a Polish Registry office. 

Polish Museum of America
This museum is located in the U.S. (in Chicago), but has a wealth of information related to Polish genealogy.

Szukajwarchiwach.gov.pl
This site allows you to search all archives in Poland about a variety of subjects. Materials include registry office records, maps, photographs and more. A limited number of these documents are online.