The only use right now is building the multiblocks for the Grinder and Blast furnace. Grinders uses Standard and Reinforced Casings. The Blast furnace heat capacity depends on the type of Casing you use to build it. Standard is low, reinforced is medium, advanced is high heat. If you look at the furnace recipes in NEI it will tell you the required heat for different ingots.
NEI won't bring up the uses for the heat rings. I would expect them to go in the fusion reactor. Speaking of the reactor, what exactly do the coils do? Do the elements fuse in them, or is it where the heat comes from?
. Strangelets are still theoretical but likely exist, they are a jumble of quarks that turn what ever they touch into strange matter (this is theoretical). Black holes, yes they exist and have been decected both in the large hadron collider in Europe and in outer space. Dark energy is just a name for the force making the universes expansion accerate. Dark matter is a super gravity that doesn't have mass, and yes neutrinos (dark matter particles) have been decected.