http://www.minecraftforum.net/topic/249637-166-optifog-and-optimine-f-hd-fps-boost/
This is for the Minecraft Beta, it really helps, especially if you have the lag spike of death.
[EDIT] -
1.7 CAME OUT
RAAAWRRR
Pistons
The largest update to Minecraft in 1.7 is the addition of pistons. Pistons - the brainchild of Minecraft community member Hippoplatimus - rapidly surged in popularity over the past few months, and were then announced by Mojang that they would be added to the official game.
Pistons are poised to change the way people build in Minecraft - we’ve already seen some amazing mechanisms come from the community, their creativity seemingly knowing no bounds.
Pistons allow the user to move blocks using redstone circuitry to control their action. There are two types of pistons: regular and sticky. Regular pistons will push a block when powered, and then retract when not powered.
Sticky pistons work in much the same way, but with one caveat: they’re sticky! These pistons will push a block away when powered, but pull the block back when retracted.
TNT Changes
TNT can no longer be triggered by clicking on it, which for most, should be a good thing! Instead, you must now use either redstone circuitry, or a good old fashioned flame to ignite the destructive block.
Shears
Shears allow you to cut the leaves off of trees in one quick swipe, as well as trim wool of sheep without killing them. Killing sheep will no longer give you wool however, just the death of a cute, blocky sheep on your conscious.
Stackable Fences
Fences have a welcome improvement for architects - they can now be stacked on top of one-another when placed in the world. This removes the need for complex block-place-remove routines, which until now, were the only way to stack fence posts vertically. Additionally, players may now place torches on top of fences.