DepositPhotos just released a plug-in for Adobe Photoshop, In-Design and Illustrator.  I haven't tried it out but it looks like a good thing for those who use both depositphotos and those products.

A new Depositphotos extension provides you with a comprehensive suite of advanced search functions, allowing you to quickly and efficiently browse millions of stock files available in the Depositphotos� collection. Not only can you buy the images you need from within Adobe� software, you can evaluate the suitability of different files before you buy them, simply by dragging the image preview to the work area of your current project. Moreover, the extension saves all your Depositphotos purchases. In order to access them, just go to the appropriate tab. Besides, our plugin gives you up-to-date information about the number of credits you have in your account and your subscription plan; you can also quickly access your credits or subscription pages via the extension to buy more or renew.

http://depositphotos.com/depositphotos-adobe-extension.html

I believe iStock and Fotolia already have one.  I haven't heard about one for Shutterstock though