So, I've been searching far and wide for the perfect filling/interfacing/padding to put into a laptop bag. I even searched this forum, and found a few topics on what kind to use, but most of it just wasn't right. No matter how thick I made it, it still felt flimsy or cheap.
I cut open a store-bought laptop bag and figured out what they used, but had no idea what the hell it was or what it was called, thus I had no idea where to find it. I eventually found the name of it (closed-cell foam) on this forum (in this post: http://www.craftster.org/forum/index.php?topic=172153.0).
Anyway, long story short, everywhere I looked it was SUPER ridiculous expensive (we're talking hundreds of dollars) and not the right thickness and blah blah blah.
Then I found this place - http://www.foambymail.com.
Cheap prices, free shipping on orders over $50 dollars, the right thicknesses, and your choice of a full sheet, half sheet, or quarter sheet.
So, I HIGHLY recommend this website for the most professional feeling laptop bag padding. It's the exact same stuff they use in store bought bags. (Just go the site, click on "closed cell foam" on the right hand side, then click on "polyethylene foam").
If you're like me and have been wondering how to get your laptop bags to feel 'right', here is your answer. w00t!
(I kind of sound like an advertisement for these people... but I swear they didn't pay me to do this, haha!)