Freecycle (freecycle.org) is one of the best known. It was started in Tucson, Arizona, in 2003 and came to the UK three years later. Now it has nearly 1.5 million users here and 485 groups around the country. The only rule is that everything advertised on the site must be absolutely free.

While some groups are tiny - Machynlleth in Wales has only 41 members, for example - others are vast: Greater London is split into 38 groups with thousands of members in each.

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