Wren - Offset your carbon footprint by saving rainforests
KOHO - KOHO is a place where you can access your money in real-time and get instant cashback.
Trip to Carbon - A carbon footprint calculation API for travel.
Paribus - Find out for free if online stores owe you a refund!
Capture - A great free screen capture utility that allows you to capture either a window or the desktop and save it to either a file or the clipboard.
TopCashback - TopCashback names itself the UK’s most generous cashback site. They offer cashback on over 5,000 retailers with a variety of payment methods including gift cards, PayPal and bank transfer.