ref card for data manipulation?

You (as many before you) have overlooked the ave() function, which can
replace the ordering as well the do.call(c,tapply(....))

Majority of questions on this list concern data manipulation. Many are repetitive. "Overlooking" like that will always happen unless some comprehensive data manipulation documentation is made.
I think many people would benefit if  a specialized data.manip ref.card were conceived. 

Tom Short's card is an excellent one but it does not cover high level packages like plyr, reshape, DoBy, and a few base data.manip functions are not there as well.

Vitalie.