surprise! you too can have your own speedtest site and you dont need much. its already out there. you can use it internally or externally. you can even connect it up to a database to remember past results. but the most important fact to me is that it is open source.
and it is available from here
first of all, you need to install some dependencies
yum -y install httpd php perl perl-CGI perl-Time-HiRes
secondly, the INSTALL file says you need to edit the speedtest.cfg. change the following to point to your server's hostname or ip address
and finally, edit the /etc/httpd/conf/httpd.conf file
<Directory "/var/www/html/speedtest">
AllowOverride all
Options +Indexes +ExecCGI
Order allow,deny
Allow from all
</Directory>