I wanted to recommend two php applications that I recently setup for our own use and was very impressed by them. One of the biggest things that impressed me about both was how ridiculuosly easy each one made the install process. Something we need to improve for the Syntax CMS open source projectwe use at work.
Squirrelmail is a great webmail front end for IMAP. Much better than Horde’s IMP project, particularly in setting it up (as I said before) but also in the huge variety of plug-ins available for it.
Gallery has a slick web-based install and configuration end, it tests your server setup to make sure which features will work. I can’t begin to list all the features here but the one that I like the most is the java applet for uploading images into albums.
I could go on and on in this post but if you have more questions leave a comment.