Getting a part-time job is the easiest way for a college student to make money. If employers are willing to hire a college student, they will usually work around a college student's busy schedule. Whether it's in retail at department store or the food industry, you'll be able to make an hourly wage to give you a little extra spending money during the school year.
Sell some of your unused belongings to get a little cash. You can post an ad on the Internet or a campus bulletin board. This is not as recurring as a part-time job, but it's a good way to free up some of your stuff and make some money.
If you're an upper-level student in a specific academic discipline, chances are, you can earn some money tutoring freshman and sophomore students who are taking lower-level classes to meet their general education requirements. If you're an English major, you can also make money by offering to proofread term papers for other students. (Note: Do not sell term papers for other students to use, as this is a good way to get yourself expelled from college.)
Whether it's mowing lawns in the summer or shoveling snow from sidewalks and driveways in the winter, there is a market in some college towns for college students to make some money by performing random tasks for neighbors and other people living around a college. Ask around; maybe you have a neighbor who would be willing to pay you a set fee for helping him or her around the house.