A couple of earlier posts have dealt with sites that allow you to determine a point halfway geographically between two others: a.placebetween.us and Mezzoman. Via OgleEarth comes a third: the Geographic Midpoint Calculator. Enter two or more locations, and the GMS will calculate the midpoint or average location (for more than two points). You can weight the locations by time you’ve spent in that city, though you can use the time-weight as a proxy for other weighting factors. Results are given in latitude/longitude, with the option to plot the original locations and average location in Google Maps.
"This site" searches Free Geography Tools; "Web" searches the Internet using Google.
There is an online tool called meetways.com that allows you to put in two addresses and a point of interest and then gives you the exact mid point and the addresses of the points of interests you selected.
Meeting Point