Piranhas will help you find the cheapest store to buy a book
Piranhas is a super helpful web app for finding the cheapest online store to buy a book. In the past, I've usually just gone to Amazon, but after putting in a couple of titles into Piranhas, i've discovered that probably wasn't the best option. Unlike similar search engines, Piranhas takes the shipping cost into account and not just the listed price. It also handles all the necessary currency conversions.
It searches all the different amazon stores (.co.uk, .de, .ca etc) as well as Book Depository and Wordery for the cheapest prices.
By far one the most useful apps I've come across this year.