I would like to do an automatic audit of bandwidth of my remote offices. I understand that there are many websites where I could ask each user to go to a webpage and run the test. I was hoping there was some software that I could run on our web server and a script that I could send out that would run the test and record the results to a central web interface. The remote sites are all running some form of Windows and the server environment can be Linux or Windows based.
You should really be doing this by having SNMP monitoring on the border router(s) of your remote sites. Tools like MRTG are made specifically for this. Except for your monitoring server, this has nothing to do with the servers at the remote sites. This is network monitoring, and should be focused on the network devices themselves.
I agree with mfinni's idea but if you absolutely feel the need to test your bandwidth you can easily create a script to use
wget to download one of those large test files from a test site.
wget's output will show what you downloaded, how long it took and the average speed for the download. If necessary run the test on a schedule.