Magento: Variables in Transactional Emails

- For registration:
{{var customer}} Will print out all customer information
{{var customer.ID}}
{{var customer.email}}
{{var customer.firstname}}
{{var customer.lastname}}

{{var customer.name}}
{{var customer.password}}
{{var customer.created_in}} Store Name
{{var customer.dob}} Date of Birth
{{var customer.password_hash}}
{{var customer.prefix}}
{{var customer.middlename}} Initial
{{var customer.suffix}}
{{var customer.group_id}}
{{var customer.taxvat}}
{{var customer.store.name}} What store they registered with (On Demo store this will display as ‘English’
{{var customer.store.group.name}} The actual Store’s name (not the Store View’s)
- To subscribe/unsubscribe newsletter:
{{var subscriber.getConfirmationLink()}}
{{var subscriber.getUnsubscriptionLink()}}
{{var subscriber.email}}

some more variables here: http://www.magentocommerce.com/wiki/modules_reference/english/mage_adminhtml/system_email_template/index