Universal Order Feed allows you to create multiple order feeds. Extension supports XML and CSV output. You can define desired data structure of final output - set tag names and type of data to be added. Extension contains all common data types + adds abbility to program own logic for shown data. Has option to filter orders by store and order status. Gives possibility to set SEO keyword for created feed. Module remembers last exported order for every feed and exports only new orders every time it is called, but you can pass extra parameters via URL and choose desired orders:

order_id - exports orders from this order (exclusive)
date_start - exports orders from this date (inclusive), format: YYYY-MM-DD HH:MM:SS

More Info:
http://www.opencartex.com/opencart-modules/universal-order-feed

NEW: Added possibility to export order products. Run install.php to upgrade database.