A while ago, I made a plugin for designing papercraft patterns. It allows you to unfold models into flat patterns, add tabs, and export them as SVGs. Just recently, I finally got around to polishing it up and putting it online. I call it Flattery, and you can get it here.
NOTE the latest version available from the PluginStore works in v2014 and earlier...
It's got three main tools for designing patterns.
The Unfold tool unfolds models into flat patterns:
the Reunite Edges tool lets you adjust the layout of the patterns:
and the Add Tabs tool makes glue tabs:
It's also got an SVG export button so you can export your pattern to a program like Illustrator or Inkscape to color and print it.