I am heading of to northern Germany and would like to continue using the inet while being there.

Are there any 3G prepaid sims available for use in Germany? Ideally, I would be able to pick them up either at the airport in Hamburg, or the train station (Hauptbahnhof).

Any response is appreciated

Best option in my opinion would be the sim card from Tschibo (They sell usually coffee). It's 10Euro for 500MB and 20Euro for 5GB per month. I just don't know how I would activate the card without a laptop and the sim is a regular size. So it would need to be cut down to fit in the iPad.

So the Tschibo SIM is not a plug-and-play card?

Here in the UK, Prepaid cards are just that, put them in and they work. If the Tschibo one requires activation, I will have to see, whether the store can activate them, as my laptop is at home.

Thank you for the suggestion.

The store will only be able to activate via snail mail.
So you would want to activate via internet. I think some Burger Kings and all of Starbucks locations should have free wifi.
You'd probably also need a valid address for registration and maybe some money to load up the card initially.

For prepaid data in Germany there are 3 different options, take a look here wiki.apnchanger.org