You Probably Know This, But...
...overclocking your PC's processor won't make your computer blow up. Overclocking can generate excess heat, which may cause erratic PC performance and, over time, burn out certain components. But even in the worst-case scenario, your system will shut down before it blows up. Newer Intel and AMD processors automatically overclock and underclock themselves, depending on how busy your PC is, to keep things cool.
. ..your cell phone isn't going to cause an airplane to crash, though the Federal Aviation Administration still has a ban on using cell phones during flight to avoid interfering with the plane's navigation and communication systems. In fact, the Federal Communications Commission instituted its own ban in 2007 for a different reason: When we're on the ground, our cell phones automatically locate the closest cell tower, but when we're 30,000 feet in the air, we're roughly the same distance from several different towers at once, meaning that multiple towers might sense our call and reserve that cellular channel for us--which could prevent other people from using the tower and interfere with existing calls.
...you don't have to worry about magnets annihilating your hard drive. Magnets were dangerous for 3.5-inch floppy disks, but modern hard drives aren't affected by anything short of a high-end degaussing device. Don't worry about your flash memory cards and solid-state drives, either--there's nothing magnetic about flash memory, so such devices won't be affected.
...you shouldn't run your laptop battery to zero. Users occasionally had to drain the nickel-metal hydride (NiMH) batteries in older laptops because the batteries would incorrectly "remember" how much charge they could hold if the user wasn't charging a battery to its full capacity. The lithium ion batteries in modern laptops, however, can actually lose maximum battery charge if they are completely drained, because doing so increases the battery's chemical resistance to recharging, which shortens its lifespan. The only time that you should consider running your lithium ion battery to zero is if your PC's battery life ratings have gone completely haywire. Draining the battery can sometimes fix this problem.
Don't Be Fooled Again
All fired up about demystifying tech-related myths? A few other sites can help.
Snopes.com is good for tracking annoying chain letters and the occasional Facebook-related scare. If friends and family pester you about such things, sending them a few links to Snopes might help.
HowStuffWorks.com has a special "tech myths" section that deals specifically with some of the more popular misconceptions in the tech world.
PCWorld Forums is also worth visiting. It's one of the best venues where hard-core PC users congregate to swap stories and advice. Ask away and get plenty of answers.