Saw this Instructable yesterday and thought someone here would find it interesting.

http://www.instructables.com/id/How-to-make-huge-posters./
http://www.blockposters.com/

Thanks! I downloaded a trial version of one last year that I used to make a large poster, but now the trial is over, obviously. This will come in handy.

Combine this with the following, and perhaps you can make some pretty good sized seamless posters for very cheap:

http://www.metacafe.com/watch/1316342/print_on_anything/