HELP: Trend reporting

Hello newsgroup buddies,

I am looking for information on trend reporting. We run Linux, PostreSQL,
Apache and PHP4. We have a series of scripts that track customer usage
through our sites, and give us similar information to what is found in the
Apache logs, but with more data.

I now find myself in the position of having to create "trend reports" or
"common routes through our site".

Any search I have done has yielded many commercial products that will do
this for me, but, unfortunately, I am looking more for a tutorial on how to
do this, rather than a product that will do it for me.

Essentially, I would like a tutorial(s) or article(s) that discusses this
topic, preferably something along the lines of my afforementioned setup (I
would like to minimize the amount of converting I have to do).

If anyone can help, in any way, shape or form, it would be greatly
appreciated.

Thanks in advance,

Jason