The Tekkit 1.6.4 build (1.2.6) has been promoted to Recommended.
Server files are available here.
Please backup your existing worlds before upgrading; loading a Tekkit 1.1.X world will NOT end well. A fresh start/new world is HIGHLY recommended, and although this should go without saying, I'll say it anyway: BACKUP YOUR FILES!
This release brings updated versions of almost all of the core Tekkit mods: Galacticraft, Atomic Science, Modular Power Suits, Minefactory Reloaded, Computercraft, Buildcraft, Thermal Expansion, and others.
We have lost a few friends along the way; Simple Power Storage, an Obsidian Plate, and Custom Lan Ports are the notable mods we've retired.
Weep not for what was, however; instead, let us celebrate what is to come! This release adds some fun and extremely useful new mods: Project Red, Big Reactors, Carpenter's Blocks, Waila, Vending Block, Extra Utilities, Redstone In Motion, and Wireless Redstone CBE (among others) are now included for your mining pleasure.