It has been a long time since the last Ajax updates, so we will start off by looking at frameworks.
Ajaxian.com just did a survey regarding the popularity of ajax frameworks and ajax platforms, and of course, the results are within expectations.
Note that PHP remains by far the most popular. Speaking of PHP, here is a comparison of 10 PHP frameworks.
If you don't need heavy-weight ajax functions, I will recommend moo.fx. For a quick demo of moo.fx, click on the "Archives" or "Subscribe" title on the right hand column of the main page. Moo.fx is relatively light - moo.fx.js, moo.jx.pack.js and prototype.lite.js weights a total of only 12.9 kb, as compared to 56 kb for prototype.js and scriptaculous.js combined.
Currently, with so much going on in the Ajax community, we also have people going COWS over Ajax.
At the Web 2.0 webfront, Israeli startup Dapper has been raising lots of eyebrows. It allows you to "create an API for any website", with some 2000 new data sources that anyone can mix and mash from sites around the web. (Check out the demo to get a better idea.)
Instead of solely creating services for the general audience, we are starting to see these type of "for developers by developers" sites. Another previous such example will be Ning.com.
Update: Over at HP, Dunn has finally resigned.