Meander, which has just hit version 1.5, is an interesting little application that lets you mark out routes on digital maps. For example, you can download maps from Google Maps or Yahoo Maps (though you're not limited to these) and then plot your own route rather than depending on the automated routing (particularly useful when you're on foot or bike). The main interface window is a translucent "Acetate", which you position over a map in a browser window (or even a PDF). You then click the snapshot button to capture the map, and draw your route. By positioning a movable scaling bar over the map scale, Meander will be able to calculate the total distance of your route, or merely the distance between any two points on the map. With Meander it's very easy to calculate distances for walking or to plot particular routes on a map which you can then save as an image file or print out. New in version 1.5 are image attachments for your route, a journal feature, and more.
Meander is $19.99 and a demo is available.