Gaia Ajax Widgets Q2 has just been released with some new features (Accordion and TreeView controls), tons of bugfixes and updates. Gaia is getting more stable in this release, in addition to the number of samples which doubled. And Frankly to say we cant ask for more from free widgets. I will personally test most of them when I had some free time(soon).
Free version (Express Edition) of Gaia is available and can be downloaded from the website (require registration). To check out what Gaia is capable of, go to their samples section or if you are interested in viewing their videos or downloading the library visit http://ajaxwidgets.com