Outlet stores are basically a clearinghouse for last year's styles. Sometimes you can find styles that are a bit older, but it's generally within a three year time-frame. For those of you that are curious, I will be putting the address of the outlet store in my questions section. The first place to look for bridal outlet centers is in your phone book. If that doesn't work, you can always try Outletbound's search features to find out if there is an outlet center in your state or area.
Consignment shops are another option.
If you are looking for a gown that is only a season or two old, this is one of the best places to look. Relatively current styles are generally sold at consignment shops, because they refuse to accept the older styles. Since most consignment shops require that the item be in good condition, you are usually able to find wedding gowns that have already been to the dry cleaners. You will generally pay more at a consigment shop specifically catering towards wedding attire, so it's always a good idea to shop at the general clothing shops first. Thrift shops can be a great place to find a bargain.