Multimine is a really simple mod and it has a feature which notch said he was implementing into the game. The multimine feature, this feature gives you the ability to start mining one block, stop and then start mining another. But if you look at the first block you started to mine it still has damage done to it. So you can go back to that block and mine it quicker rather than mining it from the start again.
This mod helps when it comes to making the most out of your pick axe. A lot of times I have started mining a block and then for some reason start mining another. I would love it if this feature was added into Minecraft because it is something so simple yet so effective.
How to Install MultiMine Mod for Minecraft 1.6.1
Download the MultiMine Mod for Minecraft 1.6.1
Download latest Minecraft Forge Universal
Delete META INF
Drag the ModLoader files into Minecraft.jar
Do the same with the Multi Mine Mod files
Close out of the windows
Open Minecraft and enjoy