One of the guilds I belong to does a challenge each year. The guild furnishes a FQ of fabric and you pay $5 if you want to participate. Then you have to make something with the FQ. If you bring it back to show, you get your $5 back.
Another guild did a Christmas stocking challenge. They were furnished the pattern for the stocking so that everyone's stocking would be the same size, but it was up to the individual how the stocking was made and embellished. Then all the stockings were displayed and guild members "voted" for their favorites by putting quarters in the stocking. The maker of the stocking with the most quarters won a prize, and all the quarters were collected and were used to buy nonperishable foods which were donated to a food bank.