ViewBug appears to have several active Photography Contests at all times. Its a great community with several different photography groups.
Each photo contest has specific types and rules as well as differing prizes per contest. Many of the contests are free though some cost but you can get around these “per photo costs” by purchasing a membership. I have found that regardless of winning there is the ability to request critiques and a great opportunity to receive feedback from other photographers!
ViewBug also has the ability to sell your photos online. Check it out!