The name "Calclavia" refers to an indie software development company, but is more commonly used as a name for the founder (and sole member).
The website may be found at calclavia.com.
The following mods made by Calclavia and are used in Voltz, or were present in past iterations of the modpack:
ICBM - InterContinental Ballistic Missiles mod
This mod adds a variety of new explosives, ranging from TNT to the end-of-the-world wormhole varities.
This mod included a number of tools for automation, including conveyor belts and robotic arms. It is no longer present in the latest versions of Voltz.
This mod is all about new ways of using science to produce advanced technologies such as fusion and fission reactors, particle accelerators, and ways to refine uranium ore into a useful fuel.
Much more about functionality, this mod adds basics such as wires and energy storage cubes.
MFFS - Modular Force Field Systems mod
Providing the means to protect your installment from the devestating weaponry added by mods such as ICBM, this mod allows you to create forcefields - providing you have the power systems to handle it!