This is a great place to visit before starting your research. RootsWeb has lots of information for beginning genealogists and experienced ones. The site is membership driven, but there's lots of free information. RootsWeb also has mail lists, including one for Harrells. USGenWeb is a huge project to put records online.
Information goes down to the county level in some areas.
If you know where your family is from, this is a great place to search.