We've saved a fortune on priceline.com for the US, UK, Turkey, France, Hong Kong.... Second the recommendation for betterbidding.com, it's been really useful.
To use the .com version you need to make your address look like a US address. If you're in Dublin, spell out the number part of the address eg Dublin Four as the address boxes won't take digits in some places. For state and zip I always just select California and put in 90210 and have never had a problem.