I've bought - and collected/saved lots of unused stamps, mainly Christmas, so as to give Christmas and birthday cards a bit of a different look.
Most of my Christmas stamps this year were from 1980 [there were many more sent but they had similar combinations]
previously - not such an ambitious project in 2010
I also make decorations and cards from old British stamps - visit my Etsy shop [though it does need stocking up on stampy things]
P.S also lots of the envelopes were recycled from a 1999 report on creativity in schools