We’ve released a radar (spider, polar) chart component for Flex as an open source (MIT) project on github. This is abstracted from our Sonarhq product. For the most part we’ve been using the Flex Charting components from Adobe, but this doesn’t include radar charts. 
We looked at several commercial packages, but these turned out to be either too expensive, or not flexible enough. There is a free component a vailable at Kap Lap, but it didn’t support the styles we needed to match the design we had.
In the end it was easier to produce our own (about a day and a half of work). The project depends on some common libraries we’ve developed at Boost over the last couple of years, which we haven’t decided on open sourcing yet, but we have included the binary under the same license so that the charting component can work. Here’s a demo and how to get going:
