A guy posted a link on the istock forum thread(Race To Silver) where exclusive contributors can copy the code from there free Moo business cards and recieve 10 free credits from istockphoto.
I got my 10 free credits and sought out 3 new contributors with no sales and bought a small file from each.
I still remember my first ever sale and i hope these three who are just starting out feel the same way when checking their istock account.