Bigasoft iPhone Video Converter is a multi-format video converter. From what I could gather using this application, it has a very good input format support. It accepted MKV, AVI, and WMV files with no problems at all. Regarding output formats, this converter can encode files into MP4 and MOV for video formats and AAC, AIFF, MP3, M4A, and WAV for audio formats. Although the video output format support isn't great, there are profiles available for a variety of different devices. These profiles optimize the conversion process for specific devices such as iPods, iPhones, AppleTVs, etc. So this isn't really an iPhone-only video converter.
In my testing, though, I treated this application as an iPhone converter to see how it managed. I used an AVI file, which is the type of file that I most usually convert for playback on my iPhone. I chose the default iPhone profile. One thing that I noticed was how fast the application converted my file. It took less than a minute to convert a 5 minute clip into H.264 MP4. The quality was also similar to that of the original file.