Ancestry.Com has some free parts but for you I think an International membership might be best (it includes US information like Federal Census *plus* overseas data that you can't get with their lower-tier membership). if you know your ggrands, get all the information NOW(names of their home villages in the old country, places they've lived in the US, if any of them served in the armed forces of the US or elsewhere, etc.) from family-members in the know. Also, you can search on ancestry.com & other sites to find [famiy-name] message boards to find others who have information and who can help you in your search.
Good luck

,
agnes!
PS - Just thought I'd throw this out there...
I have this one ancestor, named "John Farr"(1758-1844) who just seems to drop down out of the sky. Can't find out where he's from or anything about his background. If anyone reading this maybe can help?

... John Farr is my 'brick-wall' ancestor.