MediaHuman Audio Converter is a straightforward program which makes it quick and easy to convert audio files between the most popular formats (AAC, AC-3, AIFF, ALAC, FLAC, MP3, OGG, WAV and WMA).
As with many similar tools, the conversions are actually carried out by the popular FFmpeg utility. Not exactly original, then, but at least you can be sure of reliable results (FFmpeg is as good as conversion utilities get).
The program's main focus is on keeping the conversion process as simple as possible. So typically you'll drag and drop your files onto Audio Converter, choose the output format, click the "Start conversion" button, and then just wait for your files to be converted.
If you need more control, though, there are useful options to be found in the Settings dialog. You're able to decide the default output format and destination folder, for instance. There's an option to add output files directly to your iTunes library (if they're in a compatible format, anyway). And you can limit the number of cores the program will use, too; this will obviously extend the conversion process time, but you will at least be able to use your PC for other things while Audio Converter is busy.