For anyone starting out in Jewish genealogy http://www.jewishgen.org/ has tons of great info.
But most of the great info lays in the memories of your own family members. Start by picking the brains of your parents and grandparents, great aunts and uncles. They usually have the foundation and leads you need to build your tree.
From Generation to Generation: How to Trace Your Jewish Genealogy and Family History
This is one of my best books on genealogy. I've read this several times over the last few years.
Geni.com used to be great for building family trees in collaboration with other family members, and they still are, except that they recently imposed a limit of 100 profiles with free accounts. And the paid options aren't very reasonable reasonable. I hope they get bought out by Ancestry or another company with better marketing skills and pricing schemes.
I can't stress that enough.. I'm really p.o. at Geni
Could you imagine what it feels like when you one day discover some names of your great great grandparents etc., and after you enter the info and hit enter, you are told that you have a limit but you can upgrade for only $9.99/mo. bla bla?
Well, that's exactly what happened to me!
I urge everyone out there to import your family tree from Geni to MyHeritage. MyHeritage is an Israeli start-up, and IIRC i read that they are larger and more popular worldwide than Geni. Moreover, IIRC they work hand in hand with the US holocaust museum, and have a very large database of Shoah victims and ybdl'ct survivors.
It's not difficult to move a family tree, you just have to export the gedcom file from geni, and your all set!
IIRC, MyHeritage even gives you a "private website" for
your family's tree!