bonus delivery to customer (buy something, get something free)

Hi,

is there a method of delivering a bonus digital product to a customer after a purchase?

Basically, I plan to put together about 10 bonus packs (zip files). Each time a customer buys a book or ebook from my store, it should trigger a bonus, i.e. customerA purchases a book and gets bonus1... and then a month later customerA returns and makes a second purchase and gets bonus2 as a thank-you... and so on to bonus10.
What is the recommended way, if one exists, to deliver the bonus to the customer:

1. a predefined email is triggered and send to the customer
2. an extra download link appears in the customers account
3. another method

Anyone have any ideas?
Thank-you.

Have a look at thatsoftwareguy.com. I think you'll find something there -- probably free - which does what you want.

Rob

Thanks Rob... I'll check it out.