When Google Images first started, it was an under-rated revolution. The idea of a specialized search engine saves incredible amounts of time, and is generally much more efficient.
Iconfinder has taken the search to a new level, as it specializes exclusively in icons to be used in your designs. The interface is extremely simple, and the search results are displayed in an intuitive manner. The icons are displayed in large sizes so that you can see everything from the search results’ page, without having to open individual icon pages. Moreover, there are some neat ajax-enabled filters that help find the icons based on background color and sizes. With each icon, you can see the license associated with it, making it very clear from the start how to use it. In most cases, it is free for personal use. In many, you even have the freedom to use them for commercial use, no questions asked.
At the time of writing, Iconfinder boasts 167 icon sets and is constantly growing. In a professional design, you’re probably not going to be relying too much on other people’s icons. But in many cases, you need simple icons that do not play a significant role in the design, or just ideas on how to create your own.