Keep in mind that the online world has not endeared itself to all. For every person that prefers an online information and payment system, there's at least one that cries "You shouldn't have to have a COMPUTER to do BBQ!"
Some competitions offer online submission as an option; many, if not most, have an online form which is to be filled out by the contestant and sent in with payment (or payment by another means can often be arranged). But there's really no standard. I've done websites of both types for contests; it really depends on what the contest wants.