You can either organize a yard sale yourself (which is kind of a hassle), or better sell the items through ThredUp, which will pay somewhere around $2-$25 for staff from Gap, Banana Republic, H&M, etc. You can browse around to see how much different items are worth. The best thing about ThredUp is that all you need to do is pack your clothes in a box and then just ship it to them (shipping costs are covered by the company).
Apply for new scholarships and grants. A lot of students think that they are only eligible for funding when they initially apply for admission. This is a mistake! There are often new scholarship opportunities for upperclassmen, though they aren't always widely advertised. You may also be able to apply for external scholarships or grants, which are offered from groups outside of your school.