Lilypad can be programmed using a block-based program Ardublocks or text based program Arduino.
Software Installation
Instructions for Installing Arduino and Sparkfun Boards
CodeKit can be used for blocks coding, arduino (.ino) file still needs to be downloaded to device using Arduino IDE
Sparkfun Resources:
Lilypad Tutorials for using sensors and outputs
Sparkfun Lilypad Hardware Overview
If you want to purchase Protosnap Lilypad Development Board
Student worksheet for circuit planning
Intro to Wearable Tech with the Lilypad (Hope's slideshow)
Sew Electric - book and website with wearable projects ideas and instructions