http://www.moneysavingexpert.com/dea…-voucher-codes
http://voucherfrenzy.co.uk/discount-codes/
http://www.retailmenot.com/
http://www.fatwallet.com/
http://www.slickdeals.net/
And here are a few UK specific sites:
http://www.mega.co.uk/
http://www.latestdiscountvouchers.co.uk/
http://www.ukdiscountvouchers.co.uk/
http://www.everydaysale.co.uk/
http://www.myvouchercodes.co.uk/
http://www.voucherstar.co.uk/
http://www.shopcodes.co.uk/
http://www.discount-voucher.co.uk/