Dealing with left over yarn

We had a very good thread on storing needles.

So how do people deal with those little balls of yarn left over from a
project? How do you store them? They do not fit in a file folder!

Do you keep the gauge trial with the left over yarn? But, some of my gauge
trials are stitch samplers that I want to keep with my patterns, and not
with my yarns. I guess that means a cross index system, i.e., a note
attached to the yarn that the guage trial is stitch sampler such and such.

When do you just throw the leftover yarn balls to the cats to play with?

Do you sort by yarn thickness or by color?

I keep projects in progress in clear plastic shoe boxes for small projects
or clear plastic sweater boxes for larger projects. Each project box has
all the yarn for that project, the guage trials, the needles, and
instructions/pattern/calculations/charts for that project. At the end of
the project, I put the needles away, file the pattern, and . . . . What do I
do with a 1.4 oz ball of bulky yarn.

What do you do with your bits of left over yarn? Is this where the squares
exchange comes in?

For now, I'm going to put them into recycled zip-lok plastic bags. The
cross index idea sounds altogether too much like work.

Should RCTY work together to get into the Guiness Book of Records by
createing the world's largest ball of yarn, one left over bit at time?

Aaron