This is such a great site--if you're a visual person, you'll love it.
What it does is allow you to collect ("pin"–via a cute "pin it" button placed neatly in your toolbar) everything you love on the web and organize it into categories ("boards"). You can cluster your favourite whatevers (art, photographs, clothes, recipes, interiors, quotes etc) on a pretty little page, which you can share with the rest of the Pinterest world (and whomever chooses to "follow" you), and, in turn, follow any other boards you like, and pick up new "pins" by "repinning."
It's super inspiring, perfect for planning, and it's also great for picking up helpful DIYS and recipes too.