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
OSGeo is a collection of open source packages for creating maps and displaying them in browsers. Some of the projects are old and effectively obsolete, and some are newer versions that effectively replace the old ones.
Some of the tools are for building applications. For instance, MapFish is a collection of server-routines written to make it simpler for you to get your mapping data into a coherent form. It projects some background layers, then you insert your data on top.
The group has been building upon this core, which seems to have become stable in 2007. Among the newer projects is GeoMoose, a tool for mixing OpenLayers data with geographic data overlays. It's popular with real estate tax departments in state governments.
Most of the OSGeo projects are protected by generous BSD or MIT licenses.
If you're a Web programmer who loves maps, you'll find TileMill to be the greatest combination since electricity met semiconductors. The tool combines open source data with a language for controlling how the data is rendered. When you're done, TileMill will spit out all of the tiles that your mapping application presents to the user.
The core of the product is Carto, a language for describing how the fonts, lines, and colors are combined. It is, for most intents and purposes, a version of CSS. You design your maps with the same corner of your brain that you use to determine the look for your Web pages. If you want the major streets to be thicker, you bump up the number next to the CSS-like parameter "line-width."
TileMill turns open source data about the world into map tiles that allow you to customize (or experiment with) the look of your maps.