I keep most of mine in plastic spiral-bound binders. These have plastic pockets like the ones in Gus's photos.
They are
sort-of organised.
The binders have different coloured covers so I associate the colour with a set's theme - sometimes more than one theme per binder - and then try to put the instruction sheets within in order of set number (or close to it) to make them easier to find.
Some of my sheets are not in the binders because I haven't gotten around to re-organising them to fit in the newer ones. Some are also still kept in their set boxes. You can probably get what I mean by "sort-of organised" now.
The good thing is I don't believe I've completely lost any instruction sheets yet... perhaps temporarily mislaid some, though...
