Bargain shopping.
Believe it or not, my wife and I found a bunch of good deals for wedding decorations on e-Bay. She got her dress at a significantly reduced price, had the wedding at a church, we were also fortunate enough to have her aunt (whose a cake decorator) make our wedding cakes. All told we spent around $3000 on the wedding but saved probably another $5,000 or so through bargain hunting.
If I had to do it again, I would have just gone to a resort and gotten married. Unfortunately, my family was pissy about our relationship (we are a mixed couple) and I felt the need to have a full-blown wedding to show them that we are serious, not going to hide, and that they'd better accept us for what we are.