A shortcut, gestures, and button management tool. A great way to enhance how you interact with your device. Use a gesture to launch an app, hold down the volume key to make a call. It's total control, and it feels like magic.
Change the default look of your iPhone with WinterBoard themes. Video wallpaper, customized keyboards, a world of backgrounds to choose from. This should be one of your first stops to make your phone look exactly how you want it.
Tethering your iPhone without getting dinged by your carrier is one of the main reasons people jailbreak. Here's the app that'll help you do it. Warning, if your carrier realizes what's happening, they're gonna be pissed.
A keyboard extender that adds the number buttons to the top of your iOS devices keyboard. A real time saver especially if you need to input alpha-numeric information on a regular basis.
Trick your iPhone into thinking your 3G connection is actually a Wi-Fi connection. Now you can do FaceTime anywhere.
Block calls and texts from people you don't want to talk to anymore. I've been getting a ton of SMS spam lately and this is a lifesaver.
If you're envious of Android owners and their fancy lock screens, give Lockinfo a download. You can peruse the weather, time, calendar events, and more, all without diving into your phone. And there are enough themes and plugins available for Lockinfo that the sky's the limit.
Add settings to iOS 5's Notification Center. That's just one of the tweaks you can make to your device with this Springboard settings app.
Show all the open apps in a single screen for fast switching. It's Expose for your iPhone and iPad.
Put icons anywhere on the screen without having to adhere to the slide-to-fill rows and columns on your iOS device. Want icons only in the four corners of a home screen? You're crazy. I love it. Use Gridlock.
Not quite sure how to actually jailbreak your device? Lifehacker has a great series of how-tos that cover every device and iOS version. Proceed with caution!