TabToolkit ($9.99) allows you to download tabs from the Internet, and then save and catalog them to use later. I've downloaded all kinds of tabs that I listen to and study during downtimes.

You can find tabs by song name, songs by artist or browse individual artists. You can also mark your favorite tabs so you can recall them quickly. This is really handy if you're working on a song and want to recall it often.

As a little added bonus, TabToolkit allows you to upload and download tabs to and from your iPad. This means that any tab you download to your iPad can be put on your computer. Conversely, if you have a collection of tabs on your computer, you can login to your iPad and upload them. That will give you an immediate starting point.

When viewing a tab, the app's interface shows you the notes, tab, and the guitar fretboard so you can see where the notes and chords are being played. The screen automatically scrolls as the tab plays allowing you to play along without needing to manually scroll.