Here is a bunch of links to free VST plugins (instruments and effects) for expanding your FL Studio environment (or any other DAW application for that matter).
Browsing the archives for the FL Studio Tutorials category
http://renownedmedia.com/blog/free-vst-plugins-for-fl-studio/
This tutorial covers the FL Studio piano roll, and explains every facet of the interface.
http://renownedmedia.com/blog/fl-studio-piano-roll-tutorial/
This tutorial will provide you with a comprehensive understanding of the mixer interface for FL Studio. We describe every single knob/option on the interface.
http://renownedmedia.com/blog/fl-studio-comprehensive-mixer-interface-overview/
An explanation of Automation Clips in FL Studio, how to create and modify them and assign them to different properties in FL Studio.
http://renownedmedia.com/blog/fl-studio-automations/
This is an overview of the FL Studio application interface. This describes every window used in FL Studio.
http://renownedmedia.com/blog/fl-studio-interface-overview/
