If you want to see how much space your apps, pictures, videos, and the like are taking up on your iPad, you can always plug it in and navigate over to the device in iTunes. But if you're lazy, or nowhere near your computer, checking the available space on your iPad is a snap. Here's how to do it:
First, head to Settings. Then choose the General tab, and press About. You'll get a breakdown of the number of songs, videos, photos, and applications on your iPad, as well as the capacity and space available.
If you are interested in seeing what apps are taking up the most space, press Usage instead of About, and you'll get this view:
As you can see, games take up the biggest space on my iPad....:-)