Let's say I store color film in the fridge. I shoot a lot, and I rarely have time to develop, so the exposed films accumulate. Can I store them in the fridge again? Is there a problem with this method? Won't the temperature changes affect the film? I normally use films with ISO around 100 or 200?
If you have exposed film waiting to be developed, storing it in the fridge is better than storing it at room temperature. Even better than storing it in the fridge is to make time to have it developed promptly.
Here is a quote from the Kodak publication Storage and Care of KODAK Photographic Materials:
"Once you have exposed your film, paper, or material, it is important to minimize changes in the latent (unprocessed) image. For consistent results, process the film, paper, or material promptly after exposure. This is particularly important with professional color films, because they are optimized for processing soon after exposure. Storage at a low temperature after exposure will retard latent-image changes. You can keep exposed, unprocessed film in a refrigerator for a few days when necessary. Put the film in a sealed container, and allow the unopened container to reach room temperature before removing the film for processing."
Edit: I should have added - the reason for the sealed container and allowing it to reach room temperature before removing the film for processing is to reduce the chance of condensation forming on the film, which you don't want. Film should always be sealed when refrigerating/freezing. For refrigerating/freezing unexposed film, the plastic canister (35mm film) or foil wrapping (medium format film) that the film comes in should be fine.