BitrateCalc is an open source bitrate calculator for working out encoding bitrates to use, similar to the built in tool in MeGUI, but in a standalone package.
The tool allows you to specify the properties of the video/audio you wish to encode (resolution, length, framerate, container ...), and works out the bitrate you need to use given a final file size (or the other way around).
Requires .NET 3.5.
Windows XP/Windows Vista/Windows 7