D.B.
What we did was have a multi-family yard sale - running a Craigslist ad for multi-family brings more traffic, and everyone gets into the spirit of it. Call a local charity - you probably get mailers from them anyway such as Big Brother/Big Sister, Epilepsy Society, Multiple Sclerosis, etc. They pick up at the house. Schedule them for the Monday after the yard sale to pick up whatever is left. Usually you can leave things in the garage or on the porch and they will pick up even if you're not home, or maybe a neighbor can be standing by. They will give you a receipt. There isn't much of a limit for taxes - at least you won't hit it with a standard family yard sale as long as you give a reasonable value for used items. You can also try local consignment shops first - let them pick over what they will sell, and then just track things on line, going in every 30 days to get paid.
For a yard sale, just price things fairly low (the idea is to get rid of stuff) and be ready to negotiate. Understand that early birds will come 60-90 minutes before you "open" so be ready. Have a lot of singles and a roll of quarters on hand to make change, buy preprinted garage sale stickers at the stationery store, and price as you clean things. You can also throw old tarps or sheets onto the yard and put all the 50 cent items on one, $1 items on another, etc.
You'll have less guilt when you realize that all those extra things will be put to use by shoppers or charities - far better than stuff just sitting there, right? It can be a learning experience for kids - don't know their ages, but you can get them to help by making it a family activity and letting them keep the money from their own sales. Sometimes kids run a lemonade stand at the sale too.