Probably too wet and/or not turned frequently and thoroughly enough and/or not enough browns and/or insufficient aeration holes in your container floor and/or a combination of the above factors.

Slimy Okra - your user name reminds me of the bottom of my compost bin ;) -- yeah, it's not getting turned enough - I'm trying to remedy that this summer - I generally turn it every 2 weeks in the summer but the rest of the year pretty much let it sit. I use the Biostack. It doesn't have a base so it sits on a pallet, but I'm not sure what else I would put it on? I don't think I am getting enough browns in there - I guess I will work on the browns and more turning and hope for the best. Thanks.

If you leave the rotting material in contact with the ground and never turn it, it will take care of itself. It'll just take a long time, is all.

That Biostack composter is supposed to be the minimum size of 1 cubic yard, but that is just barely enough for the bacteria to properly work. It is very easy to get the small amount of material that goes into those types of composter too wet. To correct the too wet problem you need to unload the composter and remix what is there, without adding more moisture, and maybe adding more dry material to get the moisture level to that of a well wrung out sponge.
Perhaps this Composting Tutorial might be of some help.

Here is a link that might be useful: Composting Tutorial

This post was edited by kimmsr on Thu, Jul 10, 14 at 6:18

Thanks, Kim, I had read that you were supposed to keep the compost wet so I had started watering it but now that sounds like perhaps that was the wrong route. I'll cut back on the water and try to get out there to turn it more often and mix more browns in - we compost almost everything from our kitchen which I love, but it's disappointing when I try to use it and it's such a smelly dark mass on the bottom.

IMO a batch of compost only needs to be turned a couple of times, but the turning does help break up the materials and create that crumbly texture in the final product. I think your biggest problem is too much moisture though. Even if there are enough browns (there might be), too much water = not enough air = anaerobic = odors.

How often a compost pile "needs" to be turned depends on what the person doing the compost wants to accomplish or how much time one has to work on that compost. Optimally one would monitor the process and turn the material just after peak temperature which could be every 3 to 5 days. However, one could turn much more often and get good compost in 14 days. Note some commercial composter manufacturers claim you can do this with their equipment so it is not as far fetched as some here would have one believe.
But most often what I have seen when consulting on composting is quite simply the material is too wet.