Let me suggest two shining lights in the open source world; Modest Maps and OpenScales.
Created initially by a small group, a number of whom now work for Stamen Design. This is an excellent mash up solution. Yes mash up, not GIS. The API includes hooks into a number of the base maps from Bing, Yahoo etc. Google though are no longer supported. The discussion group is very active and well worth checking out for examples and release information. You’ll get quick responses to questions from the core developers who administer the list.
Figure 1 – Modest Maps Map Demo
We wrote an tutorial for Adobe, helping people get up to speed on building their first Modest Maps applications. Take a look here.
Started by a group in France, this is a port of OpenLayers to Flex (thus the name OpenScales). The earliest releases were a little rough around the edges, but things have come a long way. With the new 1.2.1 release, many of the earlier issues seem to have been resolved. Openscales being younger and, to date, less well supported is not as mature as OpenLayers. But it does provide some excellent tools for geospatial development. We have built a number of applications using GeoServer. OpenScales provides excellent support for WMS, WFS amd GML.
Figure 2 – Flex Openscales Map Demo
See a longer discussion on OpenScales here which includes a viewer whose source you can download.
Building mobile applications using OpenScales, from some recent testing, has also proved quite easy. Here is a short video showing a test application.
I’d be interested to hear from other Flex developers on other geospatial API’s. Send me a line