I hear you, Can't Say. I'm sometimes utterly lost in this huge (12 rooms, cellar, garage and porches) house I inherited. It's full of stuiff "too good to throw away" from four generations, and I'm not blameless myself. I'm working at it, but not much of a diarist. This thread does help.

Some things I've learned:

Stop buying. It seems obvious, but it's hard for me to avoid buying books and cds. I've even committed the horrible sin of copying cds to my hard drive and then selling or giving them away.

Figure out recycling. It's much easier to throw out a warped metal table if you know it'll become something useful somewhere (else).

Yard sales work on many levels. First, you have to decide what might make some money. Then you get to see what people will actually buy. I usually have a huge table of random stuff that might be of interest or use, and sell it for a quarter apiece. People love it, and I get to talk to them. Things I think might be worth a fair amount, I'll leave unpriced and try to pick the brains of the folks stopping in as I try to sell it. It's immensely satisfying to see a little kid happy with a bag of dinosaurs, or a guy snatching up an old wrench. Some folks are out to make money, I know, but they're out here looking and good luck to them. After you've dragged your stuff back in a couple times, it'll be MUCH easier to either donate it or just throw it out (though the books are still hard for me).

I've used craigslist successfully, too. My more successful sales postings have been rather chatty ("This was my mother's best set of china, only used on holidays"). I've also unloaded some unusual stuff (for example, a load of darkroom equipment) by suggesting unusual uses - I suggested homeschool experiments with the lenses) and keeping the price very low. I had no luck with books on craigslist. If you list on craigslist, you have to pay attention to your incoming email and make some decisions about trusting others (no checks).

How to start? Fill a box with random stuff, settle into a comfy chair, and sort. It'll take more time than seems right, because there'll be memories and things to think about, but decide what to do. It's ok to have bigger donation and yardsales piles than trash. They recycle much more than paper these days. And it's ok to have an "Maybe, but I just can't decide today" pile. After a session, box up the yardsale stuff and evict the trash, recycle and donate piles from your living space. Have you visited your local landfill? Many have areas for things that are "too good to throw away." My guess is you'll have a few more square feet to live in. Then do it again the next day. It can be very slow but it does work.