I've created these for one of the project we have been working on over at Threefifty. These files are free for personal and commercial use. Enjoy!
ZIP file includes 24x24, 32x32, 48x48, 64x64, 128x128, 256x256, 512x512 PNG's, as well as a fully scalable PDF file for print purposes. Free for personal and commercial use. Show us where you used it :). Enjoy!