[cute fuzzy bunny]

Whats growing in there might be above the water line in the machine. You might want to try hot water and plenty of bleach, run it part way through the cycle and then let the water sit in there overnight. A couple of cups of white vinegar and a cup or two of baking soda mixed into a hot load (no bleach) and scrubbed up inside everywhere you can reach and then left overnight might also do it.

Might be a bad seal thats allowed some water into somewhere its not supposed to be. Might also be some nasty old lint or a piece of towel/rag thats been caught up underneath something and is just rotting away.

As far as the hose attachments, little known fact...many washing machines have little inlet screens on the back where the hoses attach, and you're supposed to take the hoses off every couple of years and clean the bits of rust and junk out of the screens. Sort of like the aerators screwed into your faucets. I doubt theres something trapped in there thats causing the smell, but it cant hurt.

Any smelly stuff coming out of any of the other faucets, specifically from the hot water? Its possible under many conditions for icky smells to start forming in a hot water heater.

Can you describe the smell? Rotten eggs? Earthy/mushroomy?

Its not easy to get any kind of cleaning solution into the machine through the hoses or fittings on the back since the machines water valve has to be open for anything to flow in, and its anticipated that the inlet pressure is going to be at least 25-30psi. I guess you could fill the hose with a bleach solution and then screw it back on without spilling any.

Last ditch suggestion...good basic washing machines can be had for a couple of hundred bucks. Some of the little front loaders come with lots of rebates from the water and power companies and end up not costing too much. And craigslist is loaded with $100ish 5 year old machines. The newer ones may use a lot less water and electricity, and may do a better job of cleaning your clothes.