Food. Would you believe that a few of my mother's friends put all the food at my wedding together within a couple of hours of the wedding. Instead of a sit down dinner we did a buffet style "snack supper." They set up about four table, boxes under the white table clothes (that were borrowed) and set the trys of food up on different levels with fresh flowers mingled around the trays. There were different kinda of fruits, lunch meats, cheeses, veggies, rolls, crackers....
Buy the food and flowers in bulk. Mom got my flowers (in season) from a wholeseller close to where they live. The food was bulk stuff from Costco. You know. Those huge loaves of cheese and meat, huge boxes of rolls and crackers. It was amazing. I'll load some pictures for you. Maybe you can get some ideas from that.
Oh, and mom made the cake. And the brides maids dresses (all two of them.) Both of those things saved quite a bit of money.