Looking at your skill set I would recommend e107 CMS at http://www.e107.org/

eGroupware has all the features of Outlook with project management tools, wiki, time manager, file share access all thrown in.

And its web based so it works across platform.

It connects to POP and/or IMAP email servers and can support 100's of users on a slow server.

I replaced my web email solution with this and now use it for a whole lot more.

A great project. http://www.egroupware.org/