I really like this tool, Easy Poster Printer is a tool for print images as a big posters using a regular printer. Easy Poster Printer enables you easily to print posters of any size (max 20×20 meters). Just drag n drop your picture into the application and click print.

Easy Poster Printer also allows you to do basic image manipulations such as rotate, flip and stretch for better fit.
When you are done creating an awesome poster simply save it!

With Easy Poster Printer you can…

• Make posters of any size (max 20×20 meters) using a regular printer (A4 for example).
• Save your poster and share it with others.
• Print or Preview any page at any time.
• Load, Clear, Rotate or Flip the poster image on the fly.
• Define your poster size in Millimeters, Centimeters, Inch or even pages.
• Adjust the poster size using build-in snap algorithms for up or down size.
• See your posters as thumbnails in Windows Explorer (Vista or later only).
• Save your own custom formats for easier reproduction.
• Make high quality posters from regular images (super resample algorithm) (150-600 DPI)
• Use Drag n Drop for both data-files and image-files.
• Change background color
• Copy and Paste images directly into the poster

Link : More info & download