You can download it for free on itunes. Just go to the itunes store and click on the movies tab and then where it asks for the film studio click on Sony pictures and a list of their movies should come up and Dear John will be on there. Click on the link and it’ll take you to the movie page and you can download it from there. And then you can sync it to your iPod.

how to put dvd/movie to your ipod? I think it can help you.Cucusoft Ultimate DVD + Video Converter Suite can help you to convert dvd/movie to ipod.
http://www.dvdtoipod.us/dvdvideoconverter/cucusoft-ultimate-dvd-video-converter-suite.html
more information:
http://search.yahoo.com/search?p=dvd+to+ipod+site%3Awww.dvdtoipod.us&toggle=1&cop=mss&ei=UTF-8&fr=yfp-t-701
Also, you can get more information here:
http://www.google.com
Also, you can search some other software:
http://www.apple.com

I have used one AVCWare Video to iPod Converter and it can convert almost video formats to iPod supported format. It can convert video with fast speed and excellent output sound and image quality.
AVCWare Video to iPod Converter can perfectly convert almost all popular video and audio formats to iPod MP4 and MP3, such as convert AVI to iPod, MPEG to iPod, WMV to iPod, MOV to iPod, MP4 to iPod, RM to iPod, RMVB to iPod, DivX to iPod, ASF to iPod, VOB to iPod, 3GP to iPod.
http://www.converter123.com/Ipod-Software/AVCWare-Video-to-iPod-Converter.html
It is easy to operate. Just few clicks are OK.
Hope it useful for you