BlockPosters - create big posters
Blockposters is a great site - it allows you to take a regular picture you have and turn it in to a huge poster. You upload your photo/graphic to the site and it converts it into multiple pages. Print them out and stick them together and you have a huge poster. It is easy to use and free.
Check out the pictures below: (I love their choice of example photo - reminds me of teachers at the end of the year)