I've gathered a number websites which host free icons. They are all listed in this article.
Here are all the Free icons avaiable on Web Designer Depot. The above title link has just the icons posts from the blog.
FindIcons.com is by far my favorite site! Always find what I need and can easily see the license for commercial work. Great site!
Everyone is going google plus crazy, as they should it's a great app. Here are some icons to help you link to google plus.