Soon I have to go for a business trip and usually I prefer doing the check-in myself to avoid the ticket counters at the airports. Last year I realized that you have not just the option of printing your own ticket but a more green solution was also available proposed by Lufthansa.
You have the choice to get the e-ticket on your cell phone. Yep. You get a short message containing a web link and that's it. Click on the link (get yourself a 3G connections), get the ticket on your phone and there are bar code readers and the problem is solved. Of course, charging your phone and manufacturing the phone probably it is not the greenest solution ever but I think it is a good option.
However, in order to be sure nothing nasty will happen, I have an A5 printout of the e-ticket (for backup) as even though I am a computer scientist I have some doubts about this new solution. However, soon I will let you know how this green check-in has happened. If it is working I will never ever print my e-ticket!