Hi, I am new to genealogy and am unsure where to go next. I finally found out my great-grandmothers maiden name. As I've gathered information it looks like her mother may have come from Germany. Living in the US, where can I look now to keep following the trail? Her maiden name is Sitzberger, her mother had a note by her name as Fitzberger. Any and all suggestions would be most welcome.

You need a location as registers in Germany are part of the communities. So you should first search all documents in the U.S. (marriage, death, immigration, naturalization)

Thank you! After I do that, how do I go about finding out information on registers? Do I have to write, are there online resources? Can I do that thru ancestory.com?

Major online source would be www.familysearch.org or pilot.familysearch.org. There you find also so-callaed Family History Centers from which you can get microfilms of the registers. Finally you can contact the communities direct. They have parish registers and civil registers (starting about 1875).
Ancestry.com I think would only be a help, if somebody published a family tree which is of interest for you.