TileMill — an application for making beautiful maps
TileMill is great, I used it to style our replacement maps, since google maps decided to start charging.  Here is an example:  <a href="http://tile.ridewithgps.com/leaflet.html" rel="nofollow">http://tile.ridewithgps.com/leaflet.html</a><p>TileMill is addictive to play with, though very tedious if you don't have a fast machine with some SSD's, as refreshes take a while to reload various zoom levels to see your work.  Not much to be done there except throw hardware it.<p>Edit: I am hosting our maps on my own hardware, mapnik2+mod_tile.  I just used the slick client to create a mapnik XML file for rendering.