Microsoft's AJAX framework has been released in "early Alpha" version according to Scott Guthrie.

http://atlas.asp.net/

Scott has some info on it along with sample here and here.


Aside from the technical aspect, I thought one very interesting thing to note was this from Scott:

-- Atlas will be built using a transparent development model.  Our plan with Atlas is to eschew the traditional two-betas and then RTM model that we often use with big projects at Microsoft, and instead move to a model where we ship very often (at least once every month and often more frequently then that), get feedback as early as possible, share our ideas out in the open (even when they are not 100% baked), and above all use the broader developer community to make sure we build the right technology.

Sounds like they are giving Agile a try...