I probably wouldn't bother with ebay if you have a lot of stuff that needs to go quickly. I've been selling on ebay for several years now, and I can't manage more than about five auctions a week, and those are only the weeks where I won't be traveling and have time to deal with it, so it takes quite awhile to get rid of quantities of stuff. A few things that are of value are worth it, but not a household full of clutter.

Craigslist is relatively easy and free, quicker than ebay, but you still have to figure out times to meet buyers and correspond with them via email or phone, which takes time. And I've found quite a few who initially express interest just flake out and never call or email back a second time. That said, we sold some too-large-to-ship items like kayaks with great success on CL.

We're in decluttering mode too and are taking a full long-bed pickup truck load (with cap, filled to the roof!) to my in-laws to have a garage sale with them this weekend. They have a much better location for one than we do, and they need help hauling their clutter out of their basement, so it works out well. A lot of the stuff we'll be selling would not be accepted at the places we usually donate (tools, yard and garage stuff, construction supplies, etc), so a yard sale seemed like a good way to deal with a lot of stuff at once.

We donate clothes and household items to a local mission.

We're finding it extremely empowering to get rid of stuff we no longer need or use. It's so much easier to find the stuff we do have, the house stays neater, and since we're probably going to be putting our house on the market next year, the staging effort will be much less.

Good for you for taking the first step -- realizing something has to be done. Do be patient and don't give up; a change like this doesn't happen overnight. We've been working on seriously decluttering for about six months, and still have a long way to go, but we are seeing huge improvements. You will too!