Can someone suggest software to convert video files (any format) to 3GP of which the output is compatible with Motorola L7? Thanks in advance!

I would suggest you to check 3gpconverters.net which provides 3GP Video Converter which is powerful, useful and so easy to use. It can not only convert video files like MOV, RM, AVI, MPEG, WMV, MPEG to 3GP, 3G2, MPEG4, RM, but also convert 3GP video file to video formats such as 3GP to AVI, 3GP to MPEG, 3GP to Divx. It can convert audio-only 3GP file to MP3, WAV, RA, AAC, M4A and vice versa, and also grab audio tracks from supported video files. Happy Holidays!