I was looking for a good (free) extensive IDE and it kept leading me to Eclipse. What addons should I use and how should I configure them if I want support for Java, Java EE, C#, and Web Development w/ PHP? Any other useful addons would be gladly appreciated. Thanks!
For PHP development I recommend The PDT project provides a PHP Development Tools framework for the Eclipse platform. http://www.eclipse.org/pdt/ There is a interesting tools in Eclipse project for javascript development.
There is a download option for a Java specific build which you can download. I personally don't do C or PHP development but I know there are plugins for each.
I do recommend using t;he Helios version of the product though there have been some forum posts about incompatibilities with some plug-ins, I find it to be much faster to load.
You may want to check out myeclipse.com because they may have a custom build closer to your requirements.