Winterboard is a cornerstone Cydia app that gives you the ability to completely re-configure the interface, look, and design of your iPhone. Essentially, it gives you control over the fonts, icon display, icon name display, background, dock color, menu color, and dozens of other options that are normally locked down under iOS. 

Once installed, Winterboard is available via springboard icon (which can easily be hidden) or from your phone's settings menu, where you can select themes, options, and even optimize the PNG's for faster loading times. The nice thing about Springboard is that it gets everything right, which makes sense considering it was designed by Cydia's own Jay Freeman (Saurik). The menu is easy to navigate/understand, and you can even adjust the position of user settings based on how often you access them.

Perhaps my favorite modification in Winterboard, as plain as it might be, is the ability to change the color of the navigation menu from blue to black. In my opinion, this completely changes the look of the phone and adds a sleek touch that's otherwise missing from the core OS.

I also like that I can brighten or dim the color of the app icons and titles, depending on my mood. 

What's most essential about this app though, is that you can download a multitude of themes and mods, including native Summerboard themes. To find and install, simply browse the themes section in the packages menu, or search for Winterboard in the Cydia repository. From there, open your settings menu and select the theme you'd like to activate. That's it, you're done. Simple and easy.

Quite simply put, Winterboard is an app that you must have if you want to take full advantage of your jailbroken iPhone.