Our houses are full of them: old computers, fax machines, video players, fridges in the garage, vinyl records, unwanted armchairs - things we don't want but still work. Research by gumtree.com reveals we dispose of over £5.6bn worth of usable household items a year, including 1.35m working fridges and freezers, and 2.6m sofas. People out there want our redundant stuff - but how do we find them?

A few weeks ago, I tried to shift a 10-year-old Apple Power Mac and a similarly ancient (in computer terms) Mac laptop. Both worked, so to throw them in a skip would have been wasteful and created toxic waste (computers can contain heavy metals and chemicals). I'd checked the likes of Computer Aid International (computeraid.org) and the Community Recycling Network (crn.org.uk). Both accepted PCs, but the words "10-year-old Apple Mac" resulted in polite rejection.

So I tried Freecycle (uk.freecycle.org), an online forum where people give away and pick up unwanted stuff, free of charge. It has 4,009 communities worldwide and, according to its online counter, 3,401,532 users. I joined my local group and tentatively posted my message: "Offered: Power Mac with printer and Powerbook laptop, bought in 1997 but working fine, need to be collected." Within three hours I'd had 30 replies. Suddenly my Macs were seen as a valuable resource. Jenny wanted the laptop for her 11-year-old son who was "a Mac fanatic", while Julie wanted it for her soon-to-be daughter-in-law; Ben needed computers for his charity in Zimbabwe.

It wasn't easy to decide whom to give them to. Freecycle etiquette dictates that you don't necessarily give things to the first emailer - and you must reject anyone you suspect wants to sell the goods. I opted for friendly sounding people who could collect immediately: Andy, who'd been on disability benefit for three years, and Ruth, a cash-starved student in Holloway. Since then I've used Freecycle to shift two fax machines, a Zip drive, an office desk, a child's desk, a malfunctioning Hoover, some kitchen shelves, a washing machine and my local vicar's sofa bed. Our fridge-freezer went to a woman with cancer who was on a special diet and needed it for her store of juices. Our rubbish was helping someone fight for life.

Then I visited SwapXchange, which offers items to swap from all over the country via its website (swapxchange.org). I exchanged a juicer and a Kenwood mixer for a bottle of organic wine apiece. The site offers anything from a therapy couch in Kenilworth to a garden shed in Bath; items wanted include a tumble dryer in south London and a garden bench in exchange for a piece of commissioned pottery in Wiltshire. SwapXchange started life as Swap It, a site set up in 2001 by community development worker Ellie Dale. Originally it covered just Bath and north-east Somerset, but it became SwapXchange and went national in 2004. "We were the first swapping site in the UK," says Dale. "Our aim is to have a SwapXchange for every area. It's ideal for house clearances - one man had a huge collection of radios and we found a home for them all."

My local SwapXchange has shifted more than 14 tonnes of items, says Islington council's Charles Dent. "In fact, we've just had two houses swapped on the site; at the other end of the scale we've had a toaster swapped for a bottle of real ale."

Another way of getting rid of belongings is via Gumtree (gumtree.com) - a popular online classified website which is free to use. Owned by eBay, it has sites in most major UK cities, Ireland, South Africa, Australia, New Zealand, even Poland. It claims to have 100,000 new ads each week. I could put most of my household junk up for sale here, swap it or even give it away. User Claire Crutchley had two fridges she didn't want: "I posted a listing and another family collected them within 25 minutes of it going live." Then, of course, there's eBay - the auction site and grandaddy of them all.

However, there are some things even these online exchanges can't shift, including our old kitchen sink, left rusting in the garden. Luckily I found a scrap-metal trader on the street taking stuff from skips and persuaded him to have it. A battered BMX bike with deflated tyres and shot gears proved equally problematic. Finally, I left it on the street corner with a note saying "Take if wanted": it went after two days. Charity shops are grateful for cast-offs (most don't take furniture or electrical goods) or try car-boot sales: there's a definite frisson in getting 50p for your old X-Files videos.

If you're still unsure about how to declutter, try national charity Waste Watch (wastewatch.org.uk), which will provide details of organisations in your area that can recycle both home and workplace waste, including computers, electrical goods, metals, paper and glass. Spokeswoman Tina Gillies says: "It doesn't matter how you declutter, as long as you avoid adding to our waste mountain. Giving stuff away or swapping it can feel great, but if you make a bit of money out of it, that's fine, too." And if nothing else, our front gardens will all look better without rusting vacuum cleaners, sodden sofas and bits of discarded kitchen.