crafts | envelopes (it's a problem)

i collect envelopes - below is a sampling from my box. i won't tell you how i've ended up with such a collection because it usually involves some selfishness, strange maneuvers, and somewhat sly questionable behaviour. but i can't help it because i love envelopes. here are all of the things i use them for:

mail art
snail mail
envelope templates
craft packs 
letter writing sets
gifts
greeting cards

i'm not quite sure what i want to do with that last group i've been collecting - maybe a journal of some sort?