A post especially for Laura
Well, first of all, there are always the standards from Targus. Huge variety of shapes and sizes, and some very inexpensive. They have even (very recently, I think, since I had never seen this before) started a line of slightly chic-er models, which are rather cute. This one: the "Liz" looks good, for example - especially if you want to carry a lot of extra papers in the same bag.
Vera Bradley has two very nice models, in cotton and microfiber. Both, obviously, come in a ton of lovely patterns and colors. You can buy them from this little shop on Chapel Street or from a wide variety of online sellers. I'd check ebay first because they often have some really great deals.
Also, Timbuk2 is great for comfortable, very durable messenger-type bags, and they make a whole line for laptops. The Marina looks awesome, among others.
Of course, there's always the option of buying a padded computer sleeve (like Ryan's, for instance - available from any computer store, etc.) and then just throwing THAT into a larger tote bag or the like.
Ummmm . . . can you tell that I SO do not want to spend all day packing???