Computer battery broken? No problem! Just weld on a 12V boat battery. 70 pounds is a bit much for a "portable computer," but it's better than no computer at all!
3 U Penn students developed the µWave (microwave, get it?), an Arduino based kitchen hack that plays Youtube videos while you wait for noms. Once you set the cooking time the program goes to Youtube and finds a highly-rated video for the exact length. Read more about it at the project's website.
Instructables user hanlin_y did the math and realized that alkaline batteries are one of the most expensive forms of power that consumers can use. So he/she/it came up with a solution to power your parts even if they don't come with an AC adapter. With a wall plug, wires, and bamboo strips you can run your electronics off the grid; saving money and the environment at the same time.