Some days ago Yahoo! launched My Travel on Yahoo! Travel with an interactive map, where you can add the places you have been to and places where you will go. You can also append some notes to the cities.
I like that idea and some time ago I started a similar My Map on Google Maps with cities I have lived and cities where I have been to.
One thing I am missing when using My Maps as well as Google Maps for this purpose is the lack to ad a period of time. In my opinion it would be very useful to have the possibility to mark when I have been to these cities or when I will go there. Then not only there could be this map with the towns, but alternatively the cities could be displayed in a timeline.