Here is a step by step guide to rip DVD and convert any videos to other video formats and audio formats for iPod touch/classic/video/nano, iPhone, Zune, PSP, video capable MP3 players, etc. Meanwhile, it can also support output almost any audio/video format including Video format (H264, MP4, WMV, AVI, MOV, RM, 3GP, flv, SWF, mpeg-1, mpeg-2, VCD, SVCD, DVD, etc.) and Audio format (AC3, AAC, MP2, MP3, MP4, RA, WMA, etc.). It is easy-to-use and the converting speed is fast!
http://www.freedvdripper.org/dvdvideoguide/dvd-video-conversion-guide-with-ultimate-dvd-video-converter.html
Also, you can find some other software:
http://www.ask.com

iPod accepts mp4 video detail as follow
MPEG-4 video, up to 2.5 Mbps, 640 by 480 pixels, 30 frames per sec., Simple Profile with AAC-LC audio up to 160 Kbps, 48 kHz, stereo audio in .m4v, .mp4, and .mov file formats.
You can lear more from: http://www.apple.com
You need a converter to help you convert the DVD to MP4 format.And then transfer the video that be converted to iTunes.
I always use iskysoft DVD to iPod converter.You can download it from:
http://www.iskysoft.com/dvd-to-ipod-windows.html
for mac users:
http://www.iskysoft.com/dvd-to-ipod-mac.html
Then ,You can directly transfer the MP4 format files to iPod using iTunes.
Open your iTunes, click “File” from the upper left corner, select “Add file to library”, browse your computer hard drive and find the MP4 format files, select the songs you prefer, click OK and the video will be put in your iTunes. Then you can just transfer the MP4 format files to your iPod from iTunes.