For anyone who plans to travel with United Airlines, I have an unused 10% discount voucher. It is valid till the 27th august 2009 (you are required to buy a ticket before this date, but the date of the flight can be later).
First come, first served, this voucher should be only valid once. If you have used it, please write it as a comment so that this post can be updated.
All the conditions and the code are detailed in the document here: United Airlines 10% Voucher.