One of the things that interested me was to find my family tree which got only till my grandmother's parents.
Within few hours research on the web I managed to dig down 4 more generations. I have to say I didnt have the same luck other branches of the family so I guess its a matter of luck, and how rare your surname is.
First, I used the Yad Vashem's victims database to get all the information known on family members :
http://www.yadvashem.org/wps/portal/IY_HON_Welcome
Then, I found the following database to be the best site to conduct such research :
http://www.jewishgen.org/jri-pl/jriplweb.htm
Apparently, this site has extensive database of records from Poland & Ukraine and has very good coverage of Boryslaw and other towns. The main information you can get there is birth/marriage/death records but also other surprising data. As an example, I found a water bill my grandfather's father has not paid in 1942 with the address of the house. Some tips for searching your ancestors :
Start with narrow search - Put all the information you know in the search fields - if you found, it just saved you hours of going over endless lists.
Broaden your search - you may find out that your ancestors were signed correctly or incorrectly in other towns or by other names.
Dont assume you are writing the names correctly unless its very distinctive - use the "sound like" feature to get better results although it can bring you lots of irrelevant names.
Do this iteratively - once you find a relative start using him as a basis for other searches. This way you get to his parents, brothers, sisters and children.
A person may have several names - a hebrew name, a polish name, a nickname, etc. so you'll need to do some name matchmaking to get things correlated to information you already have.
After getting the information it can become pretty difficult to keep track and you end up asking questions like who is the sister of the grandmother of the daughter of your uncle. In order to avoid this, you can manage a family tree with one of the web/software tools available. Two such tools I found useful are http://www.geni.com/ and http://www.myheritage.com. The latter has also a software based tool which can be convenient to add a lot of information. It can also sync the information to the web.
Here is a sample report of my ancestor tree with MyHeritage :
Water Bills query results :