Here's a really nice seed for Hardcore players to get started quickly on (Default world type):
-4763277371877247586
You start in a jungle. South-east is an ender forest and a cave with visible gravel, copper, coal and mithril. Close to the cave is a lava pit for fueling your early smelter. A few paces south west of this cave is a rocky outcrop with more ores including aluminium. There is a pumpkin field in the forest too, allowing you to set up stone golems for early game defense.
Further east is a flat plains area with plenty of food around. There is a Better Dungeons tower just south of the redwood tree, and a wicker man east of the tree.
Overall the best seed I've found so far.
Edit 1: In the ender forest cave is a lot of Deadly Worlds spawners including a flaming arrow spawner, so be careful. There's loot to be had if you're ready to fight the spawns though.