AniMap
This excellent family history software program displays over 2,300 maps to show the changing county boundaries for each of the 48 adjacent United States for every year since colonial times, plus listings for more than 799,000 places in the United States (including more than 120,000 variant names).

Deed Mapper
An impressive program for analyzing old grants, patents, deeds, and claims.  Purchase the appropriate maps and start plotting!

Farmer's Plotter
A Macintosh deed plotter for genealogists.   This is an ftp site with a demo download of the commercial software.

Guide to Citing Maps & Atlases
How to document maps in your research, from the Lloyd Reeds Map Collection, McMaster University Libraries.

How Far Is It?
Calculates distances (as the crow flies) between cities around the world.

Maps in Family Research
Donna Przecha introduces a variety of map types from around the world which are useful to a genealogist.

More Than One Kind of Map
George G. Morgan discusses a variety of different types of maps you can use in your family history research, including some you may never have considered.

Topographic Maps - The Basics
The Centre for Topographic Information of Natural Resources Canada offers an excellent introduction to topographic maps and how to read them.

Using Maps in Family History Research
Donn Devine offers a great overview to the different types of maps useful in genealogy research as well as related techniques, such as land platting.

Using Maps in Genealogy
This article by the U.S. Geological Survey explains how to get use maps for clues to where our ancestors may have lived and where to look for written records about them.