Windows: Handbrake is one of the best video converters out there, but its interface leaves a lot to be desired, particularly if you're converting a large batch of videos. Free app Smallx264 fixes that with an easy-to-use approach to the power converter.
Download and install the app and you're ready to begin -- you don't need Handbrake installed on your PC. Just drag-and-drop your videos, select the output file, and choose from one of the presets: Android tablet, Apple TV, iPad or iPhone. Advanced users can fiddle around with all the video settings Handbrake allows, like bitrate, audio channels, and filters like deinterlace (and save these as a custom profile). Plus, you can trim the video if you want and see a quick preview before you hit the 'Start' button to batch process all the videos in one fell swoop.