If you're a comfortable and curious php coder, you're not even likely reading this and have already dug into my functions file.
If you're a little familiar with php coding and really want to change some aspect of your portfolio, beyond what's already been discussed, then take a look at the portfolio_functions.php file in your portfolio_app directory.
All screens for phpPortfolio are in here. It's fairly well commented, function names are descriptive, functions are grouped in a somewhat logical manner. Layout and logic styles are consistent throughout, so learning how to change the layout of the table for lists of clients for instance, will pretty much teach you how to do it for all similar screens.
Of course, editing things in the portfolio_functions file will make it much harder to apply any upgrades in future versions of phpPortfolio.