I've been wanting to look for a way to open multiple pages as my start page using tabs in FireFox. I thought that there was probably an extension available to do this so I looked on their extensions page and came up empty.
Then I did a regular Google search and found something very interesting. Apparently FireFox has this ability built into it. All you have to do is separate the pages you want opened with a pipe ( | ) and voila!
So, for example, my start page setting looks like this:
http://www.fites.net/index.php|http://www.msn.com|http://www.gmail.com|http://brainwashes.blogspot.com|http://www.myspace.com
Just thought I'd share this discovery with my FITES peeps. Enjoy!