A straightforward web interface for geocoding addresses in a CSV (or other delimited text file) and visualizing the results on a map as you go. Spits out CSV and GeoJSON. [more inside]
Metropho.rs is a geographic metaphor map that plots "X is the Y of Z" tweets by putting the "Y" label on the "X" location. Some nice coverage by the Atlantic Cities blog here. [more inside]
Tweetchive is a little web hack I made to show your past tweets in various views. The primary view is a map, there are also views of pictures and text and links. It's not really a finished product, but it's useful enough I launched it. [more inside]
With an accompanying intro and arty blog post, Project it Yourself rethinks map projections and lets you make new ones from scratch, with nothing more than household math.