I've not used Pigsback, so can't comment on the points scheme, except to say it looks better than Nectar. ;)
I discovered today that Suttons & Unwins offer cashback via quidco.com... If you ever shop with any of the high street or online 'big names' you'll probably find you can earn cashback via the Quidco site. (Sadly, Amazon is a notable absentee.)
