Xycraft is a new tech mod for minecraft. It is still in early stages and is nowhere near finished. It has a lot of potential and may become one of the best mods out there.
Xycraft actually adds a few ore blocks and quite some technical blocks. Although it is not finished, we can take a sneak peek of them at Direwolf20's Season 4 SMP server play.
The ores added by xycraft:
Engineering blocks which forms different multi-block structures (muli-tanks and stuff)
Automatic crafting tables