Just a brief list of free tools for Ajax web development:

• Dojo, the Javascript tool kit
• Prototype Javascript library and framework
• ASP.Net Ajax - Microsoft’s Ajax framework

And a couple of cool online calendars:

• CalendarHub
• Kiko

Last but not least, a summary of a presentation by Adam Bosworth, Google’s VP of Engineering, on the past failure and current success of Ajax:

“…in the end, AJAX got a second life, primarily because the physics changed” - Adam Bosworth