In reply to doug5_10: The smell is made by bacteria so basically anything that kills bacteria will help. Most of the things mentioned so far should be effective at killing bacteria:
heating
using acids (e.g. vinegar)
using alkali (e.g. baking soda)
cytotoxic substances - e.g. silver, alcohol
Freezing them might kill some bacteria but I'd guess it's the least useful way mentioned.
You can also stop the bacterial buildup to begin with by:
- Removing shoes between climbs to allow them to air and reduce moisture in them.
- drying shoes immediately after use on radiator or similar, rather than throwing them in a sack and leaving them in a constricted space with no air movement.
- keeping your feet cleaner, there are a bizillion ways to do that here:
http://www.wikihow.com/Get-Rid-of-Foot-Odor
Personally I just go with not caring very much ;D