Format Factory. It's free. The interface is simple but it's also widely configurable.
*www.formatoz.com/index.html
Here's a quote from the site:
Format Factory is a multifunctional media converter.
Provides functions below:
All to MP4/3GP/MPG/AVI/WMV/FLV/SWF.
All to MP3/WMA/AMR/OGG/AAC/WAV.
All to JPG/BMP/PNG/TIF/ICO/GIF/TGA.
Rip DVD to video file , Rip Music CD to audio file.
MP4 files support iPod/iPhone/PSP/BlackBerry format.
Source files support RMVB.
List of Ver1.80 changes
1. Added "All to MKV".
2. Added H264,DIVX,XVID codec advanced configuration.
3. Added supporting of H264,DIVX,XVID 2 pass encoding.
4. Added Video,Audio file's split and preview function.
5. Generate THM files automatically after PSP MP4 converted.
6. Fixed WMA encoding problem.
7. Added several language files to support up to 45 kinds of languages.
8. Fixed some problems of video merging.
9. Improved DVD Ripper function.
10. Added aspect ratio of the video file configuration settings.