Overview on how to use special Technic parts? I just came out of my "Dark Age" inspired by my kids growing up and getting more and more out of Duplo and into Lego. I bought a mixed lot of Technic parts and man, there are a lot of new parts!

So the question is: Are there any resources on how a part is typically used? 

E.g. how are this 2 parts used?
In general, the best strategy would be to look up instructions for a set in which the piece is used. 
Also a good strategy: ask here ;)

For the specific parts you mentioned, this picture might be helpful:



The 6641 element switches a driving ring in three positions, either engaging the left clutch gear (18946), the right clutch gear or neutral position in which neither is engaged... 

My favorite set these elements are used in is is 8043:



This set has 4 motors, however one of the motors is used to turn switches consisting out of the discussed elements to ultimately provide 6 functions: left &amp; right driving and turning the upper part on one position of the switch, while operating the digger (bucket, middle arm, lower arm) on the other position.