For me there's no attachment issue, it's more a problem of logistics. I have tons of stuff that I plan to get rid of, but I want to get rid of it responsibly (both fiscally and socially/environmentally). That means not just hauling it out to the curb for the garbage collectors, and that slows down my purging considerably.
So far, I've taken the followng tactics:
Books: I've cut my book collection by more than half over the past five or six years. In the past I would read a book and if I loved it I'd keep it so I could read it again someday. But 90% of the books in my collection are books that I've read only once, and some of them are books I read once 20 years ago. Most of them are available from my local library if I ever do decide I want to reread them. So out they went. I sold a dozen or two on Amazon, sold a few boxes to local booksellers, tried (without success) to donate the rest to libraries and bookstores, and ended up giving them to Goodwill.
CDs: I'm a pretty serious musician and have a large CD collection, a few thousand. They're all in boxes in the basement and because we listen almost exclusively to music on the computer or iPod these days, those CDs have stayed in their boxes for the past five years. So most of them are going too -- it's harder (but not impossible) to sell CDs on Amazon, but mostly I'm giving them away to friends. The ones I can't give away will be pitched; I don't have time to try to sell them as there are too many.
Clothing: This one's easy: if I haven't worn it in the past year, out it goes to Goodwill. I do a purge every change of season.
Photograph albums: I scanned the photos and slides I really wanted to keep, and now they're all stored on my computer (and I keep an offsite backup). The originals went out in the trash. That got rid of a few boxes.
Electronics: Old computers, modems, disk drives, etc. have a way of hanging around after they're no longer being used. I found a small nonprofit in my city that takes this old equipment and finds new uses for it either in local nonprofits or they ship them to developing countries. So I donated most of my old electronics to them and got a tax deduction as a reward.
Paper files: I used to save all kinds of articles, stories, whatever caught my eye as something I might like to read in the future. Over a couple of cold, wet winter weekends I went through all those files and got rid of more than 3/4 of them. There's a shredding service in town, so I boxed it all up and took it in to be shredded (some of those files were things like ancient electric bills etc. that had my name and address on them).
Hardware and equipment: I remember once going to a yard sale and seeing a big red pulley and thinking, "oh, I could use one of those someday." I hauled that pulley around with me for a decade or more from apartment to apartment, and it finally dawned on my that I would never find a use for it. I've got quite a few things like that in the basement, and again I'm just waiting for a rainy weekend to go down and look at it all with a cold, fresh eye and get rid of the things that realistically I will never use.
It's true that occasionally I've gotten rid of things that I end up having to buy again a few years later when the need arises. And it's true that occasionally I've gotten rid of a book that I end up missing later on. But those are rare exceptions. The overall feeling I get from my purging of stuff is one of lightness and freedom. But boy, does it take time. It would be a lot easier to just have someone haul it away and be done with it, but my conscience would knaw at me knowing that all that stuff just went to the landfill when it could have been useful to someone else.
