Multiple versions of same post for my mobile site

Hi, I have a little problem and it would be great if someone could help me.

What I want to do is have two versions of each post. One for my main site and one for my mobile site. I need to do this because the main site posts have to much information and images for mobile site, so I want a cut down version post for them. Hope I have made my self clear, say if not?! There might be a plugin that I haven’t found or PHP code that I don’t have the skill to edit.

Help greatly appreciated.

Ben