Sadly I've used up all my invitations but I signed up the waiting list and I think it was only about a week before I got my invite.It's just so handy. You create 'Boards' (think pinboards) and then pin stuff to them. This is my 'Embroidered Beautiful' Board. (You can see it in real life by clicking here.)
Then this is my 'OMG I want a cat so much' Board. (Click here for more.)
You add stuff by adding a shortcut button to your favourites menu bar and when you see an image you like, even if it's mixed up with a tonne of others and a load of text, you click the button and it isolates the images and asks you to click on the one you like. Then you select a board to pin it on and away you go.
I've always wished there was a way to categorise my Flickr favourites as well as a better way to collect lovely things together than just bookmarking the whole page. And here it is!