You have a lot of options for this. Since your switching out equipment completely this wouldn’t be a bad choice to go gigabit since that will soon replace 100mbps.
If you know how to use Cisco equipment, a Cisco 4500 would be my choice. Otherwise, Juniper has a new line of switches which seem to be easily manageable. I suggest you do some research and figure out which equipment vendor you would personally feel confortable in managing.
Take a look at this <a href=”http://www.technick.net/public/code/cp_dpage.php?aiocp_dp=guide_networking_switching”>tutorial on network switching</a>. Get some basic network education like the <a href=”http://certification.comptia.org/network/”>Network+</a> learning.