Drag and drop files in Firefox and Chrome to convert them to base64 strings.
If dropping images, right click on the thumbnail for the data URI.
Features (or, "What makes this so cool?")
encodes any file into a base64 string
easy drag and drop of files on your computer into the drop zone
works offline; files aren't uploaded anywhere, so your sensitive data is safe
for Firefox, no server needed, just open index.html from your file manager
very portable; entire tool is contained in one file (index.html)
previews images as data URIs, for easy copying into CSS
Mozilla Firefox 3.6+ or Google Chrome 6+ (maybe Opera 11.1+ and IE10+ also?)
Open index.html in your browser. Firefox doesn't even need it to be on a server (Chrome can only get the file info, but can't read the file to convert to base64, so either copy to your local web server or use the online version).
Drag files from your file manager into the drop zone.