There is only one website that I can think of, and use regularly, and that has to be Thresholds.
Of the competition submissions I have entered I have found 80% of them on this site. Of those submitted one in five have given me either contacts or I have been placed.
But they don’t just do competitions, they will tell you about any submissions. They also have an audio section and a resource area. The site is linked to The University of Chichester and has the nicest people running it.
Need to chat with someone about an issue?
Well, they also run a Facebook page that works like an open forum. They also put submission deadlines on there as they come up.
They also run their own competitions and will take submissions for their online website.
I definitely recommend them… Have a look!