Create a website or blog about a topic that is of great interest to you and other students, such as college sports or life on a college campus. Promote the site by distributing fliers around campus and posting notices in the student union. Work with the college's radio station to see if you can promote your site on the air. To generate revenue from the site, use services such as Google AdSense to post free pay-per-click ads. Place affiliate links on your site where you earn a commission whenever someone purchases the affiliate's products. You could also sell advertising space on the site to other students.
Create your own products and sell them to other students. If your field of study is graphic design, use your expertise to create T-shirts and sell them around campus. You could also take orders from students and make customized T-shirts. Create a website to generate additional sales. If you have access to some storage space, sell items on eBay to raise money. Check with other students for unwanted items that they're willing to give you for free, or offer to split the commissions with them. Build your product inventory by scouting yard sales and thrift shops for inexpensive items.
Turn your car into a rolling billboard by selling advertising space. Companies such as DrivenMediaOnline.com will pay you to place magnetic signs on the side of your car that advertise a product or business. If you park your car on campus, you may be advertising products that appeal to college students such as electronic gadgets or fast food. If you commute several miles to classes, you'll likely be advertising products with a wider appeal since you may be traveling up and down busy highways. Legitimate mobile advertising companies will not charge you a fee to sign on with them.