I too, love pelican cases. For my foam-taming needs I use the following:
1) the pick& pluck that comes with it. - CAREFULLY measure the size you want, pluck it out and then brush it lightly with CA glue and that stuff will hold up a lot longer.
2) If you can get ahold of foam, use the pick and pluck to make a template, then get a piece of foam large enough to cut to fit and an electric carving knife ala jon's post. You can get cheapo electic carving knifes at most good hardware stores (think *ace* not *home despot*) and foam can be had by checking the yellow pages.
A competitor with Pelican who have some great products (Especially for tool management) are B&W cases. Similar pick and pluck, but they make some downright sexy tool cases.
Oh, and don't like the hard glued edges of the pick and pluck, or the color of your foam? find some nice fabric and glue that shit to it! instant sexy-case!
"TO DO IS TO BE" - Nietzsche
"TO BE IS TO DO" - Kant
"DO BE DO BE DO" - Sinatra