Pinterest just keeps growing and growing. Ever since last year, the new social network has exploded. It's still not big enough to be household name like Facebook or Twitter but it's on its way there.
The site has also become a huge traffic driver, but only for certain types of sites. Sites which use a lot of images, sell products or have tutorials seem to be benefiting the most.
I know UltraLinx has been benefiting hugely from Pinterest, sometimes beating Twitter in terms of referrals. I've found that infographics are hugely popular on Pinterest and because the post view in Pinterest is quite narrow, people end up clicking through to see the bigger picture.
If you aren't on Pinterest yet, you really need to be. Becoming an early adopter will benefit hugely if the site does blow up to become as popular as sites like Twitter. You'll have a huge bunch of followers and people will be pinning your content massively.