This tradition varies by location. In some cities they are rampant, in cities just 20 miles away they may be taboo. Why not start the tradition in your town for this great idea?
Depending on where you live, these parties may be called a Stag and Doe, a Stag and Drag or a Jack and Jill Party. The couple may host this party or the attendants may do so as well. In these parties guests are invited and charged a small admission. There are door prizes, raffles, food and music. The money made from admission, raffles and any other games or contests is then given to the bride and groom to help pay for their wedding, honeymoon or whatever they could best spend the money to do.
All the rules of invitation etiquette apply when hosting these events. You can never mention gifts on the invitation. It is best to spread registry and other gift information by word of mouth. Only people invited to the actual wedding should be invited to these parties to help the bride and groom avoid uncomfortable situations. A wedding may be just one day, but it can be celebrated for a year or even more!
Read: Pre-Wedding Parties | Showers | Last Stand Parties