Quantum Generators by Denfop, ijo42
IC2 193+
Quantum Lights by DarkMorford
A large-scale light source.
Quantum Minecraft Dynamics by lach_01298
A Nuclearcraft addon that aims to bring particle accelerators and particle physics to minecraft
Quantum Stars by Rouhol
QuantumFlux by Jotato
Wireless Redstone Flux
QuantumStorage by Gigabit101
Quark by Vazkii, wiiv
Small things.
QuarkStudio - Core by QuarkStudio
Quarry Craft by bor295
a mod initially made to provid some purple and gold decorationblocks grown out to be a quarrymod. weird huh?
QuarryPlus
QuarryPlus is an add-on for Buildcraft that adds Advanced Quarries and various other items
Quartz 'n' Steel Mod by redstoneCircutor, baddaspig
A simple mod that adds a few more quartz-related items! - Original Version
Quartz Mod by Spicy_Killer, MCreator
Quartz Plus
Adds quartz ore to the overworld which is useful for when you don't have access to the Nether, and adds quartz tools and smoky and rose quartz variants.