Pinterest, not being new, is generating tons and tons of visits to other websites.
It is a social network very well oriented to image impact.
You can find a very useful blog post by Enigmacypher here.
Once you create your boards on Pinterest and share your images, (or whatever images you want to share), they are available to be re-pinned by others who enjoy them.
The best way to promote your portfolio and also be the referrer for that image is editing the pin. How to do it?
-Go to the image you want to share, open tools tab and copy the referral link you find in the bottom.
-Click Pin It Button (red dot with a P on it).
-Select the board you want to pin it to, edit the text if needed, and Pin It rectangle button again.
-Click on See Your Pin button.
-You will see your pinned image and an edit button. Click on it, then edit the link on the box, by selecting it and pasting your referral link for that image.
-Hit Save Pin and your are done.
Not editing your pin is good as well, but you will not be the referrer if a new buyer or contributor registers after following your image.
This is also good for promoting someone else's work with your referrer link, if you are, lets say, a buyer. You can trade your future referrer cash to credits you can spend on new images.
If you are not yet on Pinterest and want an invite, let me know so I can send you one.