If you think about odd collections, make it easy: EVERYTHING is collectible.

The guy with the biggest collection of sea-/air-/travelling-sickness-bags sits in Alaska. He got one item from me. A sickness-bag from the Danish railways from 1987. My sister brought it home from a school-exchange (unused of course). I kept it for 20 years and then I thought, if mybe someone would like it. So it was.

Be alert and check, what you have in your clutter, or what you have inherited from grandma. Think about http://news.yahoo.com/1-000-old-chinese-bowl-sells-over-2-233804822.html
This had happen before. At the -really good- flea market in my first hometown Hannover someone had bought a little drawing for 3 D-Mark (1,50€). It was an original Picasso.