What I'm wondering is how - ph.otogra.ph - online photography project managed to get such a domain name.
Does anyone know how I would go about doing this?

.ph is the country extension for the phillipines so technically this site should be registered in the phillipines. They register the domain as otogra.ph and then create a subdomain ph which when put together becomes ph.otogra.ph

del.icio.us is another example of this. the domain registered would be icio.us and then the del subdomain is added.

It's a creative way to use domains as domains are getting harder to find. del.icio.us was the first site I really noticed doing this. I'm not sure if they were the first, or more likely just the first to market it well. It's a great idea I think. It's easier to come up with memorable domain names though you may run the risk or people not knowing where to add the dots.

Ok thanks for the info
I might have to look into getting one for myself

Glad to help. I like the creative use of the domains and would probably go with one if I could think of a good one. They seem catchy to me, but I think you do need to be careful about people forgettng where to put the dots when typing things.

They can be catchy though and do open up a lot of possibilites for new domains.