i use imtoo mpeg encoder ultimate it will convert just about anything to anything and the default settings just work.
i use to convert avi/xvid to ipod, gives good picture and sound on ipod.
ImTOO MPEG Encoder is an ultimate video and audio format converter. Whether you're encoding MPEG for DVD production or extracting audio from video files, the program makes conversion from one format to another quick and easy.
The program supports large numbers of video and audio formats such as DVD, VCD, SVCD, VOB, AVI, DV, MOV, animated GIF, swf, MPEG4, RM, WMV, ASF, WAV, WMA, MP3, 3GP, m4a, mp4, h264, raw YUV, MP2, ogg, m4v, AAC etc. With it, you can extract audio from video files or remove audio from video files.
ImTOO MPEG Encoder supports batch conversion even if the files in the list use various settings or have different target formats. Before encoding, you can preview the original files through the preview window. You can see the file properties and settings without opening another window. All settings can be easily set in the interface.
The program allows users to choose a start point and file duration if they want to convert a clip. All codecs are built-in. The software makes conversion between so many formats a breeze!