ukaskew do you manage to sell many of your photos?
Not through Smugmug so much, I think maybe 4 or 5 lots from there, it's quite akward as it looks easy to buy from there but then you realise it's all US based, I publish me email address on the front page and most enquiries come straight through that. When I get a request I put them on Photobox and do it through there.
Quite a few from Flickr though, got an album cover out in the US in a few months and had some positive feedback from some interesting folk (such as Mosler), seems like a good place for it as everybody is on a level playing field, you can't hide behind a fancy site, it's just millions of images all on the same webpages.
Haven't really figured out a way to properly sell them yet, I just sort them out as and when the emails come in. I've never actively chased a sale or ever actually offered them up, people just ask. Doesn't seem to be anything UK based to easily do it that well. Custom sites linked to a Photobox ordering system would be awesome.
Going back to Flickr I find it pays to tag your pics well, get some decent keywords on them and they seem to do their own thing, nothing happens instantly, certain pics that have been on there for 6-12 months just seem to gain interest all of a sudden.