For the US, the Censuses are usually my first place to check. While you do have to pay to have access to them all, and nicely indexed online, you can often find them on locality websites.
All the censuses after 1850 show every family member.
For example, there's a website I use alot that is all related to the New River area of Virginia/North Carolina. There they have several area censuses transcribed:
census - Google Search
Cyndi's list is a good place to look for locality websites. Also, most counties have Genealogical Societies, some of which publish great stuff...so google
________ county genealogical society to find ones in areas your rooting around in. Other good sources in the
Sticky. Be sure to check that out...especially for the 1880 Census which is free and indexed.
Remember, though: Counties were added alot - and boundaries changed - from census to census...so when searching them, be sure to keep in mind that what county your ancestor lived in may have been called something else in an early census.
For outside of the US research, googling is your best bet for freebie info. You'd be surprised what search combinations of
last name city county area country genealogy will net you.
Now, have you done
this yet?

I'm not psychic, but I do know: If you dig into your family tree and don't, you will soon wish you did.
It's very easy to learn - and I'm happy to help you get started using it if you find the directions daunting. It will make the whole thing so much more enjoyable and manageable.