Cameron's questions:

If I have two Meganiums in play does each leaf energy count
as four?
If Ditto uses Riptide from Lv. 69 Feraligtr does
each energy in the discard pile count as a water?
Will a Rainbow energy count as Dark and Steel?
If you discard Recycle with Com. Search, Energy Retrieval,
Item Finder, Oak, ect., does it com back to your hand?
If you have two SlowKings in play do you have flip 2 coins?

Answers:

No, you can't get 4 grass energy from 1 card.  Here's what
the power says:
"As long as Meganium is in play, each G Energy card
attached to your G Pokemon instead provides GG."
Each grass energy CARD (the keyword here) provides
two grass energy.  If the power stated "each G Energy
provides GG Energy" then I suppose you would get the
multiplicative effect you were thinking about.  But alas,
it does not say this.

Energy in the discard pile cannot be treated as any type by
Ditto.  Here's what his power says: "...you may treat any
Energy attached to Ditto as Energy of any type."  The
keyword here is ATTACHED.

Yes, Rainbow energy can count as Darkness and Metal
energy...they are basic energy TYPES, although their cards
are not basic energy CARDS.  (So Rainbow counts as the
type, and will not give the added benefits of actual
Darkness and Metal energy cards.)

You must mean Recycle Energy.  No, it doesn't go back to
your hand.  It must be "IN PLAY" when discarded to go back
to your hand...this means attached to a pokemon.

Yes, a player would flip twice if he/she had two slowkings
in play...he's very nasty!

hope this helps,
Willy Wonka
jcm6y@virginia.edu