These days, most bags can accommodate most laptops PCs up to 15.4 inches; like the really cheap American Eagle messenger bag. When I got this bag (model no longer on sale), I didn't even think I will be using it to carry my books and notebook PC; it was though as a EDC pack to when I have to run some errants in the city. It doesn't have any good features besides a small zippered pocket inside and another front pocket; but it does the job of carry your stuff plus a computer really well. In the picture, you can see how a 15.4" Sony Vaio fits quite nicely, with a little room to play.
|EeePC 1000HD inside portable DVD player sleeve.
|Old AE messenger bag with 15.4" Sony Vaio.
Now; if you want a more dedicated computer bag, the options are almost endless. Like the computer/messenger bag; in this case, the truly awesome Bag of Holding by thinkgeek.com. This is a great example of a really versatile bag in the messenger style. It has a excess of pockets and compartments that can hold a lot of stuff in a organize manner without breaking the bank. Sure, there are better bags out there, like the Maxpedition Mongo Versipack or a Saddleback Leather Company briefcase; both of which offer the best versatility, quality and style but at a higher price.
|ThinkGeek's Bag of Holding.
But wait, I'm a backpack kind of guy/gal. Well; you're not left in the cold either. Like in the messenger bag configuration, there're many, maybe to much, models of backpacks designed to accommodate your laptop too. Most of then can hold computers up to 15.4" inches but some of then also come with a pocket big enough to accommodate laptops with bigger screens; like this Toshiba Qosmio X505-Q890.
A good pick in this category is this Burton backpack, from their White Collection. This pack is really versatile and affordable. When a got it in November 2008; it was really affordable. For around $40 bucks you get a cool looking piece of gear that also have good features all around. Another great selection for the ones that can't make up their minds about what kind of bag to get are the bags that I call hybrids.
|Burton's White Collection Backpack.
|Targus Brilliance Convertible Messenger Notebook Case
This bags offer two or more carry methods. One of the more affordable ones; without compromising to much quality, is the Targus Brilliance Notebook Case. This bag fits up to 15.4" notebook computers and can be carried as a backpack as well as a messenger bag. Apart from the laptop compartment; it also has lots of room for books, documents and other gadgets that you may need on a daily basis.
In the end, a laptop bag is a subjective purchase. Apart from style or any fashion statement; it has to be functional for the task at hand and perform its duty day in day out. It is true that most people don't need one; but, who wants to mess up that beautiful finish? A good craftsman always takes care of his tools.
Update: Here are some video reviews:
Bag of Holding video review by Youtube's thedevirkahan.
Maxpedition Mongo Versipack video review by Youtube's RoscoeBa.
Saddleback Leather Company Briefcase video review by Youtube's jpschubbs.