>> Photos, mostly of Bath (city and campus) and ducks
Pickle is like flickr (photo albums with tagging / social networks), only more so. You can add video as well as still images, and (here's the best bit) you can create unique email addresses to which you and others can send photos, to upload them into an album. So, for example, after that amazing party, when you're really hoping somebody took a photo of the incident with the absinthe and the inflatable penguin, you get your guests to send their photos to something like firstname.lastname@example.org, where you can caption the photos, organise them, and generally do what you like with them (though blackmailing people with them is deprecated). Or something like that. I mean, give me a chance, I only signed up yesterday.
My initial impression of it is that it's no quicker than flickr (which is a shame, as that would have made a great tagline) but has a nicer UI -- I haven't played with flickr much, but that's partly because it doesn't feel that intuitive to me. Pickle claims it works 'like email' but the interface looks more like "My eBay" to me, though that's not a bad thing.
If you want to know more, read the Techcrunch Review ... or just dive in and try it!