This thread on Polycount I came across today is super useful. A great range of awesome tools that make polypushing and artwork that much easier and less tedious.
The one I've come across that has made things easier is a print screen tool named Greenshot. There's some neat features that allow you to screenshot a specified area of your screen. Then you have the option of either copying it to you clipboard, upload to imgur (yes!), opens in image browser or save and some others. Boy does it save time.
PaintersWheel is a cool extension for Photoshop CS6 (also CS5) that extends the standard colour picker functionality into something more robust. You can pick two colours and generate a range from those two colours as shown below.
PaintersWheel CS6 Link
Also not so much of a tool but Flickr, for me, has proved to be one of the best image search engines from anything from portraits of WW2 soldiers to abandoned buildings. 90% in super high res too.