Wow - check it out... Aptana (the "other" IDE for web development) just got support for the Microsoft Ajax library.  The Microsoft Ajax Library is that the core of ASP.NET AJAX, but does not require any Microsoft software on the server of client.  And now, not even in the IDE. 

 

 

Hanselman has all the details, including the com.ajax.ms.3.5.21022.8.jar that you just drop into Aptana's plug in directory.