What’s that site that frames screenshots in iPhone/iPad/Mac stock photos

The built-in application is called Grab. You can find it under the Utilities folder in Applications.

You can also use keyboard shortcuts to take screen shots. Here's a quick guide from Apple:

In Mac OS X, you can use simple keyboard shortcuts to do all sorts of things, including capturing images of what’s on your Mac screen. For example, you can take a screen shot of your entire screen by holding down the Command and Shift keys and pressing a 3.

If you hold down the Command and Shift keys and press 4, Mac OS X turns the cursor into crosshairs you can use to select whatever portion of your display you’d like to capture in a screen shot.

If you immediately hit the Spacebar after typing Command-Shift-4, Mac OS X replaces those crosshairs with a little camera. Using the camera, you can take a screen shot of the Dock, the entire menu bar, a single open menu, the desktop, or any open window.

1. Use Image Capture to import the pictures to your computer.

2. In iTunes, connect and select your device, then in the Photos tab select the folder that you put the photos when you imported them.

3. Press Sync.

Once you've done this once, it become easier. You already have the folder set up in Image Capture and in iTunes, so all you have to do is…

1. Connect your iPhone (you can set up Image Capture to open automatically when you connect your iPhone in System Preferences).
2. Click Import.
3. Connect your iPad and click Sync.

Alternatively, you could purchase an iPad Camera Connection Kit, then use a USB cable to connect the iPhone directly to your iPad and use your iPad to import the photos.