You can do a ton of great things with just an iPad, but some of the best uses are using it as an external controller for your computer. From using your iPad as a second display to turning it into a remote, here are a bunch of ways to augment your computer using an iPad.
Use Your iPad as a Second Display
It's still debatable whether or not a multiple-monitor setup is productive or not because it really boils down to what kind of work you do. That said, an iPad makes an excellent extension to your monitor if you don't have a lot of space.
You have a bunch of different options to turn your iPad into a second display, but we prefer Air Display as the easiest option. With Air Display, you install the app on your iPad, and another on your Mac. After a reboot, you'll be using your iPad as a second display within seconds. For a little more customization and power, Splashtop XDisplay is another great option that works a little more smoothly than Air Display, but the set up process isn't as intuitive.
Turn Your iPad into a Keyboard Shortcut Machine
Keyboard shortcuts are tough to remember, and even if you have a grasp on the basics, certain programs have so many shortcuts and actions it's impossible to remember them all. If you want to extend the reach of your computer's keyboard to you iPad, you have few really solid options.
If you want to just test out if this is a feature you'd want, HotKeys is an app that allows you to easily control and use shortcuts on your iPad to control your Mac. It's a little awkward to set up, and it's not foolproof, but once it's running you can create sets of shortcuts that work in specific applications that are all accessible on your iPad.
For power-users, we like Actions for iPad ($3.99) because it can do pretty much everything you throw at it. Want to just use it for quick access to hot keys? That works out of the box. Want to add specific action buttons, like "New Tweet," or "Quote Tweet" to Twitter? You can do that too. In fact, you can customize all sorts of actions, including hotkeys, snippets, control media, move windows, control the system, and even open specific web pages. It take a little while to set the whole thing up, but once Actions is running it's like having a super powerful extension to your keyboard.
Finally, if Photoshop is all you really care about, then Adobe Nav for Photoshop allows you to get quick access to all your Photoshop actions in one place on your iPad. It's not perfect, but if you're a frequent Photoshop user it's worth checking out.
Use Your iPad to Remotely Control Your Computer
Remote control apps shouldn't be that exciting, but controlling your computer remotely with your iPad is one of those experiences that's pretty exciting to do no matter what. You have a ton of options here to do remote control.
We like Screens as one of the better options. With it, tapping into your computer remotely is easy, and you get full multi-touch control when you're in. Essentially, with little set up you'll have complete access to your home computer from anywhere on your iPad.
Screens is expensive, but you have a lot of other solid options including, Jump Desktop, LogMeIn, or Mocha VNC that offer a similar experience depending on the features you're looking for.
Use Your iPad as a Trackpad or Remote
Not surprisingly, you have quite a few options for turning your iPad into a trackpad, mouse, or general remote control for your computer. We have a few options for doing this we like depending on exactly what you're looking for.
If you're looking for a general purpose trackpad, we like Mobile Mouse. On a basic level, Mobile Mouse turns your iPad into a trackpad mouse with multi touch, but it does a ton of other things, including, application launcher, working as a file browser, media remote, web remote, presentation remote, numeric keyboard, and more. Essentially, it turns your iPad into a smart track pad that can also operate as an extension to your keyboard.
For a slightly different experience, we like JumiDesktop+. Alongside a similar set of remote control features, JumiDesktop+ turns your iPad into something closer to a mouse, as well as a keyboard, a remote desktop, and a ton more. iPhone users looking for a similar program will also want to check out HippoRemote Pro.