Sorting through junk is one of those problems that everyone in the world has. However, most people use a very inefficient technique. It goes something like this:
- procrastinate until you have a mountain of crap so high that you can't see out the windows anymore
- wait until a Sunday when you feel really productive
- lock yourself inside and slowly work your way through the entire pile
- manage to throw out 15-30% of the stuff, giving you another month before you collect enough junk to require doing it again.
I'll call this method in-place garbage collection.
Now, when your pile consists of things that are obvious keepers, or obvious junk, you can do this very fast -- you just zip through the pile keeping or discarding everything -- no deliberation necessary.
However, when it's not obvious whether something is needed or not, the problem gets much more complex. You now have to compare each item to every other item and assign it a rank on a "usefulness" spectrum. This requires you to remember the usefulness of every item in the pile to every other item in the pile, so that you can mentally give them a rank in your head (in other words, you have to do an in-order "usefulness" sort in your head). The rank of every item tends to change as you go through the pile too, some things seeming less important relative to others.
This is not something that our brains are good at. 
I've discovered an easier method of sorting through junk. It goes like this:
- procrastinate until you have a mountain of crap so high that you can't see out the windows anymore
- wait until a Sunday when you feel really productive
cherry pick the things you know you want to keep, and the things you know you want to throw away
- put the rest of it in a temporary place
- if you ever need anything, go get it from the temporary place
eventually, throw out everything in the temporary place!
I'll call this the lazy incremental sort, since it doesn't actually sort out the middle items right away -- an item is assigned a rank only if you ever actually need to use it. After a certain amount of time, you can then dump everything in the temporary room!
This technique is very similar to the One Laptop Per Child project's method of saving files. They call it The Journal (click that to read all about it -- it's genius!).
Basically, The Journal keeps everything that you ever input into the computer and sorts it chronologically. If you decide you want to keep something forever, you flag it as keep. Otherwise, as you run out of disk space, old things are erased to make space for new things.
It's similar to the way our brains store information -- old memories that aren't accessed frequently just fade away. You don't have to sort anything -- just keep track of the stuff that you use frequently.
Good idea, huh? 