Not as pins themselves, but if you will tap blue 'i' icon (visible when the pin is tapped), you can save the location as either a bookmark (accessed via the book icon at the top) or a contact (accessed via the Contacts app).
You can go to the Map app from the Contacts app by tapping on the address field.
Neither of these save the map data, only the location. That means that without 3G service you'll most likely end up with a very accurately placed location on a blank map. Not terribly useful. The app does have buffered maps, but the space is limited and you can't control what has been buffered. For a single trip it is possible to create a route, zoom in and view the whole thing, and use it for the trip. However any further use of the map when you access the internet again will likely overwrite the buffer.
To be certain that you have offline maps you need to get an app that stores it's map data locally on the iPad. I use Copilot. Other's recommend Navigon. The only free program I am aware of is NavFree. As far as I know all of these apps can save favorite locations for navigation to or from.
