If you’re a college student, you may find that you’re having a difficult time coming up with cash to pay for things that you need, such as gas, food, and textbooks. Even if you have a part time job, you probably aren’t able to work enough hours to make as much money as you need. Here are some ways to make extra money while still having enough time to go to classes and finish your homework.

1. Sell Books. Half.com is the best place to sell textbooks that you no longer need. You can also sell other books that you have laying around on half.com. If you aren’t able to sell certain books on half.com, there are also other places that will buy used books from you. Websites like powell.com and cash4books.net offer money for used books and even pay for the postage to ship your books to them. These sites can be picky about what they will buy from you, however. If you are unable to sell certain books online, try brick-and-mortar used bookstores like Half Price Books.

2. Sell other items. You can sell more than just books using online auctions and free classified website. Other than the well-known sites like eBay, there are plenty of niche auction sites out there such as gothauctions.com and free non-auction classified sites such as blujay.com

3. Tutoring. If you are exceptional at a particular subject, helping other students could be a great way to make some extra cash. Just be careful not to let yourself fall behind in your own classes while trying to help others succeed.

4. Babysitting. A lot of people would prefer hiring a college student to babysit their children, since college students are generally more responsible than high school students. After you put the children to bed, you can use the time to study or work on homework while you wait for the parents to get home.

5. Sell Plasma. This option might not be a good choice for those who are squeamish around needles, but there are many blood banks that offer cash incentives for plasma donations. You can earn $120 a month and help save someone’s life by donating plasma.

6. Online Writing. While you probably won’t get rich, you can make some extra money each month by writing articles for websites such as triond.com.

7. Get an On-Campus Job. Most colleges have jobs available for students. While you will have to set aside a few hours each week to work, the fact that you’d be working on campus will save you travel time and it will be easier to schedule working hours around classes. If you have classes a couple hours apart during the day, this could be an excellent opportunity to make money during the time that you would be idling away on campus anyway.

8. Become a Secret Shopper. While a lot of the “secret shopping” companies out there are scams, there are legitimate companies that will pay you to shop. Secret shopping can be a great way to make some extra money. If you choose to do this, make sure you research the company you are planning on shopping for before registering on the website (if a company charges any money to become a member, it is, without exception, a scam).

9. Start a Blog. You can make money from blogging via advertisements from programs such as Google AdSense or by selling products on your blog from affiliate programs like Amazon Associates. It will take a while for your blog to become popular enough to be able to make any amount of money from it, however.

10. Recycle Aluminum Cans. While you won’t make much from this at all, you might as well recoup some of the money you spent on the soda in the first place. This is also a great way to help the environment.

11. Be a Lab Rat. Volunteer for paid psychology studies. If you are willing to be studied, you can make some extra cash. Check around for studies at your college, as well as other nearby campuses. I would not recommend drug studies, however, as experimental drugs can cause harmful side effects, but psychology studies can be fun and are unlikely to cause any physical harm.

12. Odd Jobs and Day Labor. You can offer to do random jobs for people such as yard work, cleaning, building things, etc. Tell people you know that you are available for such work, place ads on your college’s social networks, and look for ads from people looking for help with such projects.