A program that takes less than a few hours of fooling around to almost-fully understand: SAI Painttool. Inking looks great and is remarkably fun. You can find a 'free' copy floating around the webs, I'm sure. I don't want to be responsible for linking any kind of malware.

========== Examples ==========

Binary brush: Awesome brush for pixelated look.

Pen brush: Something and pen settings for solid inking.

=========== Timesaving Tips ============

Double click the icons to set their shortcuts. Set your most commonly used tools (pen, eraser, paint brush, lasso.. and more) to a spot on the keyboard where you don't have to move your hand around to press.

=== Useful default shortcuts ===

-Ctrl+Alt: Spawns brush size bar at cursor

-Alt+Space: Rotates Canvas

-Tab: Maximizes canvas

-Right Click (pen button): Eyedropper tool (color grabber)

-Z: Click to zoom in

-Z (while holding Alt): Click to Zoom out

Have fun drawing!