Calling all students of engineering! And, anyone who just loves sharing the things they've created. AutoCAD WS [iTunes Link] has just hit the App Store, and it's totally free! The application enables you to view, edit, and share your DWG files from anywhere, and it allows you to view and work with AutoCAD drawings directly on your iPad, iPhone or iPod touch. Dang, talk about mobility.
The app fully utilizes touch and gestures, so you can zoom in and out, pan easily around your drawings, and even add text annotations where necessary. This app is not the actual AutoCAD, however, so if you're expecting a full blown application, you'll have to purchase the software for your desktop, which is not yet available for Mac.