What sizes are needed?
If you were to create a favicon for every possible use. These are the sizes you would need to create:
16px: For general use in all browsers, could be displayed in the address bar, tabs or bookmarks views!
24px: Pinned Site in Internet Explorer 9
32px: New tab page in Internet Explorer, taskbar button in Windows 7+ and Safari’s ‘Read Later’ sidebar
57px: Standard iOS home screen (iPod Touch, iPhone first generation to 3G)
72px: iPad home screen icon
96px: Favicon used by the GoogleTV platform
114px: iPhone 4+ home screen icon (twice the standard size for the retina display)
128px: Chrome Web Store
195px: Opera Speed Dial
Tools to make multi resolution icons
iconworkshop/ costs $70
http://icofx.ro/ costs $40
Tools to make single resolution icons
telegraphics.com free photoshop plugin