Using what I have access to has already been the biggest money saver in planning our wedding. The price of wedding venues is through the roof . . . often costing more than the entire budget I have. They (whoever they are) say that a venue may be up to 50% of your budget. I say no, that I'd rather have it be 0% of my budget. So that's what we did.
I may not have a lot of things for a wedding, but I have a lake. One of the perks of being on staff at the camp where my fiance and I work, is that we have the option to have a wedding on the grounds. At $0, that was an easy decision for us. It's free, it's beautiful, it's our home and we get discounts on lodging for our guests. It's perfect.