At my work we host a decent sized number of client websites, some with database backends and some without. In any case we charge them based on disk usage as well as inbound/outbound bandwidth.

This stats script runs across a certain client (we break them up in the directory structure by client code) and sends me, at the end of every month, that month's activity by the client site. I have particular pride in getting the inbound/outbound data out of webalizer's raw files with awk.

You can download the script in the Downloads area.