By Phil Gyford

Photo sharing sites are two a penny on the web

Last week many of my friends were in foreign parts, working and holidaying. I may have been stuck at home but I was keeping up with the conferences, bars and beaches as photo after photo arrived at my computer, hundreds over the course of the week.

It took little effort from my friends - often pictures were snapped directly from camera phones and arrived at my screen a few key presses later - and even less effort on my part.

But last week wasn't unusual. This week I know Paul's been at his allotment, Annie went hiking with her family and Chris ate at McDonald's. I've seen all this and much more, and all thanks to Flickr.

Flickr is a small photo gallery website which was bought by internet giant Yahoo! earlier this week. Big deal, you might think. There are plenty of sites for putting photos on the web - Yahoo! already has its own. Kodak runs Ofoto, Google has Picasa, there's PhotoBox, Shutterfly, PictureTrail and dozens of others.

It's about capturing moments - things your eyes have got caught on Tom Coates

But while most photo sites tout the ability to share your photos with family and friends they have little sense of community beyond that. Flickr, however, has rethought the sharing of photos and turned it into a far more fun and sociable activity.

Flicker turns the photo-sharing idea on its head. Instead of users inviting others to peruse their online photo albums, Flickr assumes you want to make your pictures public, unless you choose otherwise. More than 80% of its 5.5 million photos are public.

Users can create a list of friends who also use the site - instantly building online communities through picture sharing. Friends can write a comment beneath your photos or even attach a discreet note to part of the image itself, turning the whole experience into more of a conversation.

This casual sociability is what makes the site so fun. Tom Coates, recent winner of a Lifetime Achievement Award for his weblog plasticbag.org, posts several photos every week from his phone and camera. "It's not about taking artful shots," he says, "it's about capturing moments - things your eyes have got caught on - and doing what you'd do to a friend if they happened to be on the street with you, saying 'check that out, isn't that awesome'".

Common interests - this is the "a day in the life of..." group

But Flickr reaches beyond friends - its archive is open to everyone, so any stranger can see your photos, and vice versa.

While you can group your own photos into themed collections - perhaps a gallery of your holiday or of your pets - you can also set up, or join, themed groups. It could be a wedding, so guests can contribute their photos of the big day, or a public group devoted to pictures of your neighbourhood, your favourite hobby, or even objects (scooters, peeling paint, muscles...).

With so many photos on the site, how do you find them? Tags. When you upload a photo you can "tag" it with a few keywords describing the picture. Anyone can search for photos matching specific tags and create spontaneous collections of themed pictures taken by all of Flickr's users. How about 21,050 flowers, 3,581 smiles or 764 photos of wind?

If you are drawn to a photographer's style, just add them to your contacts and never miss out on any of their snaps again.

As you might expect, webloggers have taken to Flickr, in part thanks to its easy integration with popular blogging tools. And, let's face it, it's easier and quicker to view a couple of dozen pictures rather than read that number of text entries.