Great open source map tools for Web developers
A rich ecosystem of free maps, free data, and free libraries give developers excellent alternatives to Google MapsFollow @peterwayner
There are also a wide variety of open data sources to drive your fun. I started poking around and was soon putting labels on railroads all over the United States. The software pulled the numbers from a large collection of open data sets.
TileMill offers a surprisingly large range of options to the map designer, and the tool makes it quite easy to produce a map with just a few clicks. The trouble is that it's quite hard to produce something beautiful. It might be cheaper to hire someone with real talent.
More mapping sources
If you're building your site or application out of the Ext framework, you'll want to look at GeoExt. The code will fill a panel with data from OpenStreetMap, then let you add your own layers and pop-ups to make the maps more presentable. The best class name may be the Symbolizer, which lets you put arbitrary vector shapes in a layer floating above the map. The code is available with a BSD license.
Most of the mapping systems serve up tiles rendered at the right resolution. It's a sound approach that allows the rendering algorithm to move quickly, but it's not particularly efficient if users zoom in and out.
JQVMap is a collection of vector outlines of the major countries embedded into a jQuery plug-in. You install it in your Web page and point the code at a DIV, which is then filled with a zoomable map. The parameters let you choose the colors and add mouse-over overlays. It's a simple way to let someone select a country by clicking on a map.
Modest Maps is a solid, basic API for putting up a map in a DIV. It's like Google Maps, but open source. You point the API at your DIV and choose a source of map tiles; Modest Maps pretty much does the rest.
HTMAPL is a jQuery plug-in that pairs HTML with Modest Maps to streamline Web mapmaking.