File system compatible with all OSes?

I use Linux and Mac OS X on a regular basis, and sometimes I have to use Windows. I need to use a flash drive on all three, and I need a filesystem that will work well on all of them. None of the ext’s work on Mac or Windows, HFS+ doesn’t work on Windows (or well on Linux), NTFS is read-only on Mac, and FAT sucks on all OSes. Is there a file system that would work reasonably well on all operating systems? I’d like it to work without drivers or additional installations, so it can be used on any computer.

What user should apache and PHP be running as? What permissions should /var/www files have?

I just spun up an Ubuntu 11.10 box and then ran apt-get install apache2 php5 to install apache2 and PHP 5 on the box. Now it is functioning as a “web server” and it loads the “It Works!” page. Now I’m trying to tighten up security and I have the following questions about linux web servers: