Recommend two JavaScript plug-ins based on eclipse

Spket (free for non-commercial users)
Main station: http://www.spket.com/
Eclipse Update site: http://www.spket.com/update/
Spket a Javascript+xml+xul plugin.
Spket supports JavaScript syntax hints, it also provides special syntax hints for a variety of popular JavaScript packages, such as jquery.
In addition to being a JavaScript IDE, the most I like is that Spket provides good support for the development of the Mozilla platform, including XUL and XBL.
Finally, of course, the license problem. Spket is free for non-commercial users, which means you can get it at the cost of losing a little bit of functionality. Or buy one with a $29.90.

Jseclipse (free)
Main station: http://www.interaktonline.com/
Eclipse Update site: http://download.macromedia.com/pub/labs/jseclipse/autoinstall/