Adobe Illustrator

 

This is a vector based program, which is based on line and shape drawing, which works alongside Photoshop in Digital Imaging.

These two resources are worth having a look at, which are accessible from this site:

Youtube - the basics you need to know

and

Online: http://www.designbolts.com/2014/08/04/50-all-time-best-adobe-illustrator-tutorials-for-beginners/

As a .pdf

Illustrator for Beginners tastytuts

As well as Sydney University course notes from my training (due January).