I've actually just found some nice codes if people want them

http://www.bjsvacations.com/promotio...al/default.asp has quite a few, ranging from the standard one-model upgrade, through to $20 off a weekend rental.

I also found that a Disney World site, http://www.mousesavers.com/rentalcar.html , has some great codes such as :

Check out the printable coupon for $20 off a weekly rental at http://www.budget.com/partners/disney.html. Anyone can use it, subject to the restrictions on the coupon (5-7 consecutive day rental required, etc.). Expires 12/31/04 and some blackout dates apply.

Wal-Mart Customers (i.e. anyone) can get up to 25% off rentals at Budget. Use BCD code W810011.

Another Wal-Mart code: Use BCD code W810000. Source: Wal-Mart edition Rand-McNally Atlas.

Get a 20% discount on full-size or larger cars at Budget if you are an American Express Platinum card member. Thanks to Margaret P for the tip.
Get up to 15% off plus a $10 off coupon for any 2-day Budget rental when you use a Discover Card. Expires 12/17/04.

If you live in New England and have a Shaw's supermarket membership card, you can get up to 25% off your Budget rental. Use BCD code X724300.

None of the codes, alas, are working within Australia, but I'm going to call Budget and see what I can muster