Look for a secondhand sofa (in your college's town, rather than your hometown, to avoid a long-distance moving hassle); plan to resell it when you move out. Other options include a futon frame plus a mattress, or a sofa that you can assemble yourself.
Consider easy chairs, which are more portable than a sofa and so may be "keepers" when you move out. Beanbag chairs win points for low price and light weight, but you may want to go with a sturdier secondhand chair, a cushioned Adirondack chair or more-packable stacking chairs or director's chairs.
Create a coffee table by adding a glass tabletop to two large terracotta flowerpots, two stacks of coffee table books, or an old steamer trunk or footlocker. Other options include cutting off the legs of an old table or desk.
Make a lamp table by adding a small glass tabletop to a stack of coffee-table books or a terracotta flowerpot. Or buy inexpensive particleboard tables and cover them with a full-length round tablecloth or a file cabinet.
Choose discount-store lighting if you can't raid a parent's or grandparent's attic or basement. Adjustable halogen and pharmacy lamps are often $20 to $50.
Bring things from your bedroom at home to personalize the living room in college. Posters, pictures, an old quilt and toss pillows make the room more homey.
Upgrade the landlord's window treatment (often plain miniblinds or pleated drapes) with a ready-made window valance for an inexpensive decorator touch.