AnyEdit plugin
Slick little plugin that enhances most of Eclipse's editors:
Project homepage: http://andrei.gmxhome.de/anyedit/
Automatic update URL: http://andrei.gmxhome.de/eclipse/
When you use the auto-update URL, you'll have to dig around until you find AnyEdit. It's in there somewhere.
I'm mostly using this to convert tabs to spaces automatically. I have it configured so that it does this automatically upon saving the file. This really only matters for XML files, JSPs, Ant scripts, etc., because my Eclipse Java formatting rules already avoid tabs.
It also supports some other slick behaviors. For instance, highlight a filename in a config file and choose Open File Under Cursor, and it will find it for you and open it. Very cool for projects with lots of config files.
Note that some editors, notably RAD's fancy "Page Designer" editor, do not integrate with this plugin. The menus don't exist and the file will not automatically be converted upon saving it. However, that's no big loss... just use the normal JSP editor and it works fine.