Like Schutzengel, I've never heard of any organisation which buys old spectacles. (There are, as Schutzengel indicates, several charities which will accept them as donations but, with a new pair of specs only costing �25 at Specsavers, there's probably no market for anyone to recycle them commercially).
To sell used stamps your best method might be to use eBay. Separate the stamps into 'definitives' (which are the 'ordinary' ones) and 'commemoratives' (which are the short term 'special issue' ones) and bag them by weight. Then advertise them as 'kiloware' (which is the term philatelists use to describe used stamps sold by weight). So, for example, you might offer "500g of kiloware, commemoratives only". Alternatively, reach for your copy of Yellow Pages, look under 'Stamp Dealers' and phone round to find out who'll buy kiloware.
Chris