Azaleas are not heavy feeders like roses are so most azaleas will be able to feed themselves with the decomposing mulch only. Maintain 3-4 inches of mulch to keep them happy. If your soil requires ammendments though, try cottonseed meal. It is organic and most local nurseries have it (not the big stores though).

HollyTone is an organic fertilizer with lots of cottonseed meal and some sulfur to help make the soil acidic. But as Luis mentioned, azaleas don't to be fed much. I recommend fertilizing in the spring either before or after or even during the bloom with a good azalea food like HollyTone at half the rate on the package. Not fertilizing is OK if the plants are healthy. If the leaves are a good dark green and you get lots of flowers, then they are healthy already.

For hydrangeas, they recommend aluminum sulfate to make the soil acid and the flowers blue. That is OK. NEVER use aluminum sulfate on azaleas. It makes the soil toxic to them. You can use HollyTone on hydrangeas though. They won't be as blue as they are with the aluminum, but it is better for the soil.

Here is a link that might be useful: How to grow azaleas.

Sample your soil and have it tested first. Your nearest [insert state here] Cooperative Extension Office can probably help with this (it seems most have web sites now, too).