I had a career in animal sheltering, and I can tell you that college students can be some of the best adopters. I live in College Station, Texas, home of Texas A&M, and worked at the shelter here. I also worked at a shelter in Flagstaff, Arizona, home of Northern Arizona University. So I've had extensive experience in adopting to students.
The benefits of having a dog at this time of your life are many as you may already have recognized. They become a stabilizer and emotional support in a what can be a very turbulent (both good and bad) time of your life. You already have the elements in place to make it work: support from family, a residence that allows pets, financial ability for proper care, experience with dogs, and a plan for your schedule.
Granted, you'll want to spend as much time as possible with your pup, but after a dog reaches adulthood, they often sleep 12-18 hours a day. When they are pups, the rule of thumb is that they can wait to pee about one hour for every month of age. So once your little guy has reached adulthood, he won't have trouble waiting for you while you're in class. I often have folks say that they don't want to get a dog because they are at work all day, but I assure you, they spend much of that time sleeping. (Keep in mind that these statements are generalities. Dogs are individuals and will have individual habits).
As for breeds, I give my vote to mutts/mixed breeds as well. I've trained dozens of breeds of dogs, and worked with adopters looking for dogs to fit their lifestyle. The first thing you want to ask yourself is: what do you want to do with your dog? If you are looking for a pal, companion, easy-going, etc, you'll look for a dog that likes to do those things. If you want a running buddy, you'll look for a dog that enjoys lots of exercise.
Often people mistakenly believe that large dogs are higher energy than small dogs, and that couldn't be further from the truth. One of the best "couch potato" dog breeds is greyhounds. They'll chase quarry till they drop, but without the prey to chase, they're pretty lazy. So large/small isn't the biggest question; activity level and favorite activities will give you the best indication of their suitability.
Also, think about breed types (think AKC groups: sporting, terrier, herding, toy, working, hound, and non-sporting). Picking a breed type that fits your interests can guide you to choosing either a pure breed or a mix (if you can identify a dominant breed type). Here's an article from the AKC site: Best Dogs for Apartment Dwellers. The AKC site has great information for specific breeds on grooming needs, activity levels, and frequent health problems (for instance: "smooched-faced dogs" can overheat easily, deep-chested ... (more)