Windows: HandBrake is many things, but a simple-to-grasp interface it is not, at least for newcomers. A simple, graphical batch encoding helper app makes lining up multiple files for encoding much more simple.
There's not much more to the app than that — it's a file-by-file video conversion tool, and it's one that simplifies HandBrake's interface to just ask you a few important questions about where your file is, where it's going, and which common format you want it in. The app is available as a helper app that looks for HandBrake to be installed (drop the .exe into your HandBrake folder if it can't find it), or as a stand-alone download that includes HandBrake and all its own prerequisites.
HandBrake Batch Encoder is a free download for Windows systems only.