Eientei is a lightweight however complex, general pack.
For technology focus it offers GregTech -- one of most advanced technology-themed mods, allowing to explore full range of industrialization process coming to be.
Based on GregTech industrial capabilities you develop, using OpenComputers LUA scripting engine you could automate any process you like, including not only basic production, but also exploring, mining, crafting, upgrade. Or just start a server-wide communication network. Or even develop your own cryptocurrency -- with Turing-full language anything is possible.
For those who are not ready to become one with the machine spirit, there is Botania to explore mystical arts and gardening vegetation, without tediousness of farmer's life.
For general enhancement, Quark provides many aspects missed by upstream developers, adding both functional and decorative aspects.
Official server: minecraft.eientei.org
Official site: https://minecraft.eientei.org