Where can I buy a cheap and cute prom dress? (online)

Try Debs they have awesome dresses for prom

Have you tried Debs? They have a great selection and great prices. check out their website
  http://www.debshops.com 

Prom? No problem saving money! I am partial to one store when it comes to young women looking their best in lower priced high fashion garments and that place is Forever 21! They have such hot items for Prom as the Front Ruffled Sheen Dress-Get all glammed-up in their strapless woven sheen dress featuring a robust ruffled front. Other features include vertical accent pleats, a distinguished waist with a removable self-tie belt, thin thread loops for the belt, an elastic smocked back, smooth lining, and a mesh-filled skirted bottom with a finished bubble hem. Hidden side zipper with a single hook-eye top closure.
- 26" approx length from top of bust to hem, 27" chest, 2.0" wide belt, 26" waist
- Measured from Small
- 55% polyester, 45% nylon, lining: 100% polyester; Machine wash cold, line dry
- Imported
Most importantly it's only $29.80! I added the information below as well as other shopping choices that are well in that cheaper price zone. Enjoy!