Stephanie Pearl-McPhee is a Canadian knitter who challenges people to think long and hard before they buy something over the course of a week. At the end of the week, during which you’ve hopefully resisted the temptation of capuccinos, theatre trips, jeans, shoes, meals out etc, you work out what you’ve saved and donate the money to medical charity Médecins Sans Frontières (MSF). Then you tell Stephanie via her blog what you’ve saved.

Since 2004, when the blog went live in response to the tsunami, $Can590,768 has been collected. She’s dubbed the initiative Tricoteuses San Frontières (or Knitters without Borders).

“I don’t care what your donation is, and I don’t need any proof that you made the donation. I believe that the planet would smite you for lying about this sort of thing,” she says.

Generous knitters send in prizes they’ve knitted. These are then sent to a random name selected from the list of recent donors.

Charities these days welcome social networking of the kind offered by Stephanie as a means of raising funds and awareness of their work.

MSF UK, the BMJ’s Christmas 2008 charity, is also getting in on the act. Inspired by Stephanie’s efforts, it has asked designers to donate knitting patterns which can then be downloaded. Knitters are then asked to put a price on the hours of pleasure derived from bringing the designs to life, calling it pennies per hour of pleasure (p/hop). They then donate the sum.

So how is the money spent? Last week two doctors who recently returned from MSF projects gave a clue at the Frontline Club in London, in a room lined with photographic images of war.

One of them was David Nott, the London surgeon who hit the headlines last year after he used instructions sent by text message to do a forequarter amputation on a boy in the Democratic Republic of Congo.

Fourteen years ago he joined MSF in Sarajevo, performing operations in a theatre lit by car battery torches. Since then his regular stints with the charity have included projects in Chad, Congo, Sierra Leone, and Afghanistan.

He was joined by Anna Greenham, who described her time in Wardher, a garrison town in the Somali region of Ethiopia. MSF is the only aid agency working there. Delivering care to the town’s inhabitants (perhaps 10,000 people, but nobody knows) is hampered by no water supply, toilets or sanitation, banditry, blocked roads, and inter-clan violence.

When MSF’s mobile clinic first opened it was like a riot, she said. A donkey cart bringing water didn’t show. Children weaned on camel milk were fed sugar water after the camel had stopped lactating. One mother had walked three days with her malnourished child, leaving behind her five other children to look after the family’s goats. Because they were nomads, how would she find them again?

The BMJ’s Christmas charity appeal raised £12,500 for MSF UK, but you can still donate at msf.org.uk/bmjappeal

David Payne is editor, bmj.com