Here are some simple icon designs. I like how easy clean they are and each one has a specific opening to it that allows the icon to be a part of the background. I also like how they are all see through and tie in well the background also.
Simple Line Icons (Free PSD, Webfont) A collection of 160 simple stroke icons that are great for mobile applications, websites and user interfaces. All icons are pixel perfect, fully scalable vector shapes released for public use.