Q:

Measuring bandwidth per site

I need to measure the bandwidth of 4 specific sites. Is there a tool free available on the net that helps us achieve this?

A:

It depends what you mean by 'bandwidth'. 
If you want to measure the available network bandwidth then a lot is going to depend on where you measure it from. And you're only going to get an accurate measurement by filling up the bandwidth. You'll also need to learn a lot about TCP tuning to understand any measurements you get.
If you mean how much bandwidth each site is using then have a look at mrtg or argus. This pre-suposes that each site runs on a seperate IP adress. For different vhosts on the same address you'd have to use something capable of reconciling protocol level information with packet level information like pastmon. OTOH if you just want a rough figure based on the content size (i.e. ignoring header size and packet retransmits) any of the free webserver log analysers should fit your needs - I use Awstats.

