Some tutorials and articles:
Boxes and Arrows
http://www.boxesandarrows.com/view/printing_the_web
Tutorial: Printing using JavaScript
http://nice-tutorials.blogspot.com/2009/05/print-using-javascript.html
StackOverflow on printing using JavaScript and dojo
http://stackoverflow.com/questions/764978/print-using-javascript
http://stackoverflow.com/questions/2396027/dojo-dijit-and-printing
Eric Meyers on A List Apart (old article but still has relevance)
http://www.alistapart.com/articles/goingtoprint/