Iron Edison Nickel-Iron Batteries! If you haven't researched NiFe batteries, it's time to take a look. These babies will last you decades, can withstand a full discharge (with no damage), and aren't toxic to the environment... ahem... Can't say that for Lead-Acid, now can we?
DIY cell phone charger (TAKE IT ANYWHERE) I have GOT to make this!
How To Clean Greasy Burners