My bitch has developed several wet patches in betwen her digits on her paws, they smell and have a slight brown sticky residue in them.
Does anyone know what this could be?

I would get her to the vets, but wonder if dogs can have athletes foot, maybe wet exzema, or  some type of bacteria? 

Our two can get similar problems, BH's have large feet and I do check them regularly for grass seeds etc (even found an small acrorn!) but especially so durring the summer as dust and dirt collects, gets damp and the skin then becomes sore, red and if left starts to weep. So check almost every other day and subject them to a foot bath containing a little hibiscrub. If weeping use sudocrem, obviously would take to vet if I had concerns. Find winter not as bad as the feet regularly get wet when out walking and they don't get as dirty and I dry them when we get home

I wonder if its a yeast infection? 

I'd agree with Justine, sounds suspiciously like a yeast infection.
BUT the only way that you will find out for sure is to take the dog to your vet.

Depending on how bad they deem it will depend on what treatment they decide to use.
It could be a mix of malaseb shampoo (anti-bacterial/anti-fungal) and antibiotics.
Malaseb is a prescription only medication so you will need to go to your vet to get it.

Hope your bitch is soon better.