Aptana Studio can be extended in many different ways. It already includes many popular Ajax libraries: jQuery, prototype, scriptaculous, Ext JS, dojo, Spry, and YUI, for instance. You can add QuantumDB, giving easy access to local or remote databases. There are run-times for Ruby on Rails, Python and PHP, and more than 1,000 third-party plug-ins to add just about any functionality you might need.
And when your project is complete, transfer it to your server using built-in FTP support, or deploy it right away to Aptana's (subscription-based) Cloud service.