You can set the store mail address in System > Configuration > General > General > Store Information.

Then, to get this setting from your module, you can use the Magento function Mage::getStoreConfig('contacts/email/recipient_email')

The function getStoreConfig will allow you to get any configuration, by giving it its XML path.

How to get a store email addres in php
What are some of the largest and most popular websites in the world written in php? I know 1 - this is wikipedia, tell please another large website.
