Upload a png file and we create 2 scaled images and then generate a combined favicon.ico for websites.
After the .ico is generated use it in your page (in root dir or with one of following rel style links):
<link rel="icon" type="image/png" href="/somewhere/myicon.png" />
<link rel="shortcut icon" href="/somewhere/favicon.ico">
<link rel="apple-itouch-icon" href="/somewhere/apple-touch-icon.png">
This works for most rails sites when you put favicon.ico in public or app/assets dir and following in the head tag of your layouts/application.html:
<link rel="shortcut icon" href="favicon.ico" />
<link rel="icon" href="favicon.ico" type="image/x-icon" />
Update: saw this got popular, will make another tool soon for barcode and qrcode generation ;). Meanwhile added pagination + caching so page loads are about ten times faster. Enjoy!