Mastering Ajax

These were posted to Ajaxian and had some useful tidbits:

3 part series on Mastering AJAX:
http://www-128.ibm.com/developerworks/web/library/wa-ajaxintro1.html
http://www-128.ibm.com/developerworks/web/library/wa-ajaxintro2/
http://www-128.ibm.com/developerworks/java/library/wa-ajaxintro3/index.html

2 part series on using SOAP with AJAX
http://www-128.ibm.com/developerworks/webservices/library/ws-wsajax/
http://www-128.ibm.com/developerworks/webservices/library/ws-wsajax2/

See the round-up of 30 AJAX tutorials for more useful information.

I'm also in the process of reading Ajax in Action which is very well written.