Tom - I would advise you to save your money, as I think it is fairly common knowledge these days that the vast majority of these competitions, are more about generating money for the people running them, than it is about promoting the work of up and coming photographers. I may be wrong of course, but I never seem to read anything good about photo competitions or the images they select. In fact I once read that some of the competitions actively select the not so good images and reject the good ones, so that their prize winning images will make more people think, well I could do better than that, so I will enter next time and walk away with the prize money, it will be easy..
But as I said this is not all competitions and I am sure some of them are respectable, but as I avoid them, I don't suppose I am best placed to give you advice on which ones are the good ones and which ones are the not so good ones.
But if you are determined to place your bets and take your chances, then go here
, and as you can see from the long and growing list, there are more than a few of these
money making schemes
competitions for you to have a go at.
Oh and I forgot to mention, you will probably find that you have also given away all the rights to your images as part of the competition rules, which you have unknowingly agreed to by the very act of entering the competition.