Best backpack for a college student?

I bike commute everyday in the Pacific Northwest, so waterproofing is a pretty significant concern for me; I've actually got two bags, and both are phenomenal, but they have their drawbacks. I switch between the two pretty regularly. I'm also really particular when it comes to backpacks...I've had a number of them. If keeping things dry is the primary concern, I would suggest getting and http://www.ortliebusa.com/ProdList.asp?scat=11. I have the larger one, and that thing is a goddamn cavern. When I was in college, it routinely held a change of clothes, all my books, laptop, notebooks, etc. Basically everything I needed for a full day out of the house, and then off to work. I use this bag as luggage. It's incredibly waterproof, and unlike any canvas bag (I'm looking at YOU timbuk2, chrome and Bailey works!) they won't mildew. If you get soaked, you can dry them off in any bathroom, and then....it's dry. The only drawback is that they don't have any internal organization other than that little snap-pouch that you can buy...and that thing is pretty limited. I would invest in little pockets and pouches for everything if you go this route. It's basically just a waterproof sack with a very comfortable back to it. Sometimes depending on how you pack it, this pack can get uncomfortable while biking, but that's only if you're lazy in packing it up. If comfort is your primary concern, especially while biking, and you don't need it to be "throw in a lake" waterproof, I would totally check out https://www.baileyworks.com/professional/super-pro/options/. This is more my everyday-all-the-time bag. I love this thing. It's super comfortable on a bike, and waterproof enough to work most days around here. It does however suffer from the mildew problem if it doesn't properly dry, like all canvas/courdoura bags. The vinyl lining keeps everything dry-ish, but again...don't throw it in a lake. This thing has pockets galore, AND a cavernous interior. If you buy one directly from them, get all the options. This thing has so many pockets and compartments that I have everything a diaper bag would have in it, in addition to my regular everyday carry stuff. It's fantastic. It's like wearing a swiss army knife on your back if you pack it right. Both bags are a bit pricy, but they've lasted 7 and 5 years respectively; Which is something like 30 bucks a year for an amazing backpack. Pretty cheap, even if you only plan on having it through college. I would NOT recommend a timbuk2 messenger style bag; they're woefully uncomfortable for long-wear-times. Their quality has also dropped quite a bit in recent years. I have an old waxed canvas one of theirs that is still fantastic, but I got a newer, larger one to replace it and it didn't last a year of hard use. I love backpacks.

For cycling, I love the http://banjobrothers.com/products/current/cycling-backpacks/. They are a great price and super waterproof. Of course, if you're just tooling around on the bike, I think a non-cycling backpack can be fine, but I don't know of many that are truly waterproof.

Try looking around local area bike shops for a deal on Chrome backpacks. A friend just got one on sale for under $100. Very rugged, great for cycling. More showy. The 5.11 tactical backpack is very rugged, but might not be as cyclist friendly. You'll find this in typical survivalist/military surplus shops that sell other 5.11 tactical stuff. This would be espcially great if you planned on using it for backpacking/traveling. Less showy.

I used to work in a sporting goods / outdoor store and you MUST go in person to try it on. It needs to be the right size for your torso & hips. You will want comfortable strap padding and wear it so that the weight rests on your hips. Be sure to weigh down the bag when you try it on (bring books and your laptop) and wear it for at least 1/2 hr in the store to be sure it's really comfortable.

Seconding Chrome bags. I've had one of their messenger bags for 8 years now, and it always keeps my laptop dry, even when riding in the rain.

Not sure if you have Vaude in the States, I know they sell the brand in Canada and the UK. I have had my Vaude backpack for three years now and it's still in really good condition and super comfy. I've used it to commute to work since I've had it and so far, it's been good in the rain (it comes with a bright orange cover that fits in its own little pocket tucked into the bottom of the pack). I've also used it on multi-day cycling excursions along with panniers, no problem.

So let's say I find a good comfortable backpack in a local store, but it's not rain-proof. Can I make it rain-proof somehow?

I'm a fan of the http://www.timbuk2.com/tb2/shop/category/laptop-backpacks waterproof "swig" style backpack. Hands down, the best non-camping backpack I've ever owned, and it's in perfect shape and still waterproof after two years of daily use, including several miles of daily walking and quite a few long bike rides. They're not cheap, but last-year's http://www.moosejaw.com/moosejaw/shop/product_Timbuk2-Lightbrite-Swig_10185402_10208_10000001_-1_ are slightly cheaper. (Also, think carefully before buying a camping backpack with waist straps. If you're not carrying tens of kg for tens of km every day, the extra weight and awkward bulkiness will only annoy you. Being able to slip you bag under a bus seat is worth a lot, and getting something that you can wear in a professional setting without looking like a crazy person may come in handy.)

When I go canoe camping, I use dry bags inside non waterproof backpacks. My current favorite is from http://www.amazon.com/exec/obidos/ASIN/B000X330D8/metafilter-20/ref=nosim/. Keeps things perfectly dry, adds little weight, and I never really worry about it.