As for myself it really depends on the mods they are installed.
No RP and no Forestry => 
for endless supply (would it be arrays or not)
RP => 
(harvesting trees => 
for charcoal)
Forestry => Bees => Free lava => 
=> profit ?
With EE2+compact solar, it's definitively solar arrays as I get the "god" state really fast.
You could just use the Buildcraft fillers ....
Lava + Water on each side of the cobblestone wall, a Filler set to destroy anything in the lower row of cobblestone (where the cobble gets generated) and lot of obsidian pipes/iron pipes to lead the cobblestone to the recyclers. Make sure you size it carefully. A fully charged filler (with maximum energy input) will be able to destroy 12 cobblestones, or even 16 with some lags on a server, before the cobblestone get generated again. 2 set of Filler will make busy a single recycler with 9 overclockers (and you cannot add anything yourself or it will overflow)
