**Update 2012-02-02 17:57 -0800:I just wrote a post about another way to do this. I really like QGIS. It’s a powerful GIS that runs on Linux (among other operating systems) and doesn’t require incredible amounts of CPU. One criticism I had of it was that it did not provide the same ‘click-and-go’ basemap experience one can get with ArcGIS for making simple maps (i.e. Add Basemap, select Bing, DeLorme, &c. and you’re done).

Google Fusion Tables is a fairly new service many may not have heard of: it lets you manage large tabular datasets in the cloud, using Google’s infrastructure. You can then visualize that data in a variety of ways, including a Google Map. The coolest feature in my mind is the ability to geocode addresses to a map on the fly. There are lots of datasets out there that, rather than providing a mappable latitude and longitude, provide an address column (or street, city, state, &c.