Aeronautical Charts App + Pilots = Apple Keynote Photo
This app allows for the display of charts in a variety of formats on the iPad; the app is universal, so it will work on the iPhone and iPod touch in case charts need to be viewed on a smaller device. The app claims to support over 50 file formats, from various image file formats, office formats, along with TIFF and PDF files. Charts can either be loaded in through iTunes Connect, or the app can sync up with Dropbox. It only uses Dropbox for downloading files, it will not alter the files on the server in any way.
Now, some of these charts can be very large files, not just in file size but in sheer resolution, due to the detail that these charts need to have. In this case, the app can pre-render files in order to make them easier to view through the app. This can either be done through Aeronautical Charts itself, with support for multitasking for continuing the process in the background while other apps are used, or through a Mac App Store app that can prerender files for use through the app.
For pilots, this app could prove to be invaluable, and can help make those iPads be usable for both Flight Control as well as flight control! Corporate Smalltalk's web page for Aeronautical Charts features more info and helpful hints for using the app, as well.