Jailbreak tools for iPhones/iPod touch
When the iPhone 3G and its 2.0 software was released, some of us thought that might be the end of jailbreaking, or opening up your device to third-party, non-approved applications (and, in some cases, mobile carriers). We thought wrong, as there were many apps worth jailbreaking for, and the process got much simpler with the Mac-based Pwnagetool and Winpwn for Windows. The greater issue is that Apple's been roundly criticized for rejecting any software that "replicates" its own apps, and is somewhat secretive about just why it kills and delays other apps, so jailbreaking will likely always have a home on Apple's multi-touch devices.
Canon Hacker's Development Kit
If you've ever been intrigued by time-lapse photography, motion-sensing shutters that can capture lightning, or being able to shoot videos of any serious length, you might not need to shell out for a semi-serious DSLR model—if you've got a Canon, that is. The CHDK lets you do all that and more, including record your photos in the very work-able RAW format, get way more on-screen information about your shots and their settings, and, as Adam put it, generally turn your point-and-shoot into a super-camera. The possibilities are vast, given the number of user-created scripts the CHDK can run. And, in true hacker fashion, you can even play a game or two on your LCD screen (while you pretend to be setting up that staged photo mom and dad want, perhaps).
Homemade Wi-Fi extenders
Sure, you could give Linksys (or Buffalo, or D-Link, or Apple, et al.) the extra cash for an extended, wider-range router than the standard box you've tucked away in the living room or office. But if you don't mind doing just a few minutes of DIY work, you can also create your own higher-powered antennas. We've covered a few ways of doing so, including tinfoil and paper parabolas, internal wiring replacements, and, for that steampunk feel, cooking strainer extenders. If you want to actually boost the power your router gives up, well, we're covering that farther down, but these are all relatively safe and damage-free ways to ensure a solid connection throughout your house.
XBOX Media Center (and its variants)
Ever since our boss bought a "classic," first-generation XBOX off eBay and turned it into a media center with the open-source XBOX Media Center, she's been using to organize all the media that makes it to her television, stereo, and other screens. In the meantime, XBMC has spawned a number of intriguing remixes and spin-offs, including Boxee, and now works on pretty much any platform that's got video cards and a hard drive—Windows, Mac, Linux, XBOX models, and even Apple TVs. If buying another whole system just to watch your downloaded videos and stream MP3s across the house sounds like overkill, use what you've got with XBMC.
A good number of folks are impressed with Apple's OS X operating system, yet can't bring themselves to pay the hefty premium for the hardware that Apple says is required for it. But since Steve Jobs & Co. made the switch to Intel processors, a community of hackers has been working to make Tiger/Leopard/et. al. run on gear you can assemble yourself, and, as Adam showed us, there's now a command-line-free way to install OS X on a "Hackintosh" PC. Checking out the benchmarks, you'll see there's not a lot, if any, performance loss in using unlicensed hardware, and the best part is you can have the case and your peripherals look however you want, and cost whatever you can afford.
Super-Router upgrades — DD-WRT and Tomato
As mentioned above, some home network routers just can't reach around all the walls in your house. And if you want to set up specific bandwidth rules—giving you, say, lots of room for World of Warcraft at night, but throttling your BitTorrents while you're actually working—you're usually out of luck. Unless, that is, you've loaded DD-WRT or Tomato on your router. We've walked through installations of both systems and toured a bit of what they can do. Plus, as many have attested, they can make a router more stable, freeing you from frequent oh-crap-hope-that-page-saves runs to re-plug your misbehaved little guy.
It's hard to say, exactly, why Nintendo didn't include DVD playback capabilities on its Wii game system, given that its games are, well, DVDs. So it was only a matter of time before a few clever folks came up with a way of getting homebrew apps and DVD playback on the Wii, without anyone having to bust out a screwdriver or soldering iron. You can add a lot more to that Homebrew Wii channel, and, if you're cool with Nintendo absolutely disliking your doing so, play backed-up Wii games on it. While you're feeling geeky, you can put your Wiimotes to use in reverse by controlling your computer with them.
Rescue old hardware with Linux
Okay, so it's not really doing anything to your hardware that a Windows installation doesn't do. But saving an older, lower-powered computer from e-cycling (or a long, slow twilight in the garage) is one of the main reasons Lifehacker readers switched to, or tried out, Linux. Seriously dated gear can often work just fine in a modern world with Puppy Linux or Damn Small Linux, and your mid-range systems—like, say, the last Dell you bought before this one—can be spun into a slick, webapp-focused system with gOS.
Rockbox and iPod Linux
Update: Added after the initial post, due to popular demand/outcry. No intentional slight intended!
In case you needed an example of Linux completely transforming seemingly outdated hardware into the new hotness, music monster Rockbox, and its games-focused counterpart iPod Linux. Rockbox is the glitzier of the pair, adding customized themes, CoverFlow-like shuffling and other current-generation features to your seemingly out-paced iPod, but iPod Linux gives you some serious freedom inside your tiny computer, and has a pretty nice roster of games. For a look around Rockbox, check out Adam's tour of the latest release.