Ok, I understand what you're looking for here. You want to grant multiple groups access to a single file (where a directory is also a file). Also, you want all files and directories (I assume) created with the default owner of the user that apache2 runs as. Correct me if I've misinterpreted you.

The basic problem with this is that Unix perms are too primitive to allow you to do this by default. As a side note, I've seen many attempts to address this problem using some variation on script glue + umask (ugly), multiple group/user membership (uglier), and directory monitoring (ugliest). Don't bother with any those.

The most elegant tool for this task would be Linux filesystem ACLs - they allow you to set multiple default owners and permissions along with the correct initial group owner. You didn't paste your fstab, so I don't know what filesystem types you have at your disposal. You can only use ACLs on ext3 and ReiserFS (I'm from BSD land, so maybe there are others that I haven't been exposed to... ).

I don't have a Linux box handy so you'll want to review the appropriate man pages or consult google for all the possibilities. For your purposes, use the tool 'setfacl':

Example:

hostname# setfacl -m g:mydev:rwx /media/data/www

This would set the additional permissions for group mydev (grants 'rwx' to the directory 'www')

To force the proper group ownership of a created file, use the setgid bit. If you have issues finding a solution, feel free to post back here. It's a lot easier to help you troubleshoot if you post your command line + output: ls -d of your current www directory, the perms of the /media/data/www (without your modifications, i.e. the default state), your /etc/group file, your /etc/fstab (or similar), getfacl output, etc.

Probably not all necessary, but I touch enough variety of systems that I occasionally forget what the defaults are from distro to distro.

Hope this at least points you in the right direction!