Because I've seen so many people doing it lately, I thought it might be good to post a little warning about this.
Be aware that using fleece as the interior layer for a cover for any laptop or electronic device can cause major issues. It can create static electricity and elicit a charge that can seriously injure your MP3 player, computer, etc and the information you hold dear. This is true whether or not your laptop is on! It also conducts heat, which is never good for electronics.
In addition to this, ANYTHING that can cause a static charge, like putting your laptop on the carpet to use, or laying your iPod on a fleece blanket etc, can do the same.
Many commercial bags and cases use fleece, so a number of people think that it's okay, but it *is not* and can completely ruin your stuff.