Would anyone know of a German SIM card with low rates for international calling back to the US? I've used T-Mobile.de in the past but international calls have been quite expensive. Thanks!

None of the mobile phone SIM cards are going to be cheap to call back to the US. If you want cheap you need to either:
--get a phone card (lots of cheap ones)(but then you need to find a pay phone or other landline)
--use VoIP, like Skype (obviously, you need a computer w/ internet)
--If you travel w/ a computer and have internet access, check out magicjack.com -- you could make free calls back to US
--Hit or miss option -- I have a WiFi phone from T-Mobile US (they call it a HotSpot phone). IF you find a free wifi connection you might be able to call home for free. I was able to do it in Rome but never quite got the right connection in Paris.

The correct answer can be found here:

http://www.fodors.com/community/euro...ne-germany.cfm

Calls to the US are 9ct/minute. Card is available for 10€ in every Lidl store or at Staples or at Jet (=Conoco) and comes with 75 minutes included.

To activate online, you need to enter some data and any german address. It won't be checked. You cannot activate the card in the store.

I asked the question about mobile phones in Germany in the thread that logos999 has referenced, so I can give an update.

I bought the card at a Lidl supermarket. It's simply a matter of going to the cashier and asking for the card and paying 9.95 Euros. You can also buy your groceries at the same time if you want. It gets a bit more complicated after that if your German is not so good.

Once you have installed the card in your phone, you must register it. You can do this either on the internet or by phone. I did it on the internet with help from our German friends. The registration form is in German but is mostly self-explanatory. You need to give a German address (I used our friend's, but I'm sure that any will do.)

On the registration, you have to choose how you will load the card--most options involve automatic withdrawals from a German bank account, but this is not necessary. You simply choose the option "Aufladung via Guthabenkarte" which means that when the card needs to be reloaded, you go to a fonic outlet such as Lidl and buy a card (Guthabenkarte)for 20 euros.

However, as soon as you have finished registering, you will get a text message (in fact you'll get many) from fonic telling you that your 75 free minutes is now available. You can then use the phone.

I've already used the phone to make calls within Germany (9 cents/min), from France to Germany (51c/min) and from Germany to Canada (9c/min). It works perfectly. Rates from Germany to European countries, the USA and Canada are 9c/min to landlines, and 29c/min to mobile phones

My German friends had not heard of this card, and tell me that it's the best deal they know of.

If you want to register by internet, you might want to look at the registration form before you leave in case you have any difficulties: https://www.fonic.de/selfcare/servlet/ActivationInfo

You will find the number (freischaltungsnummer)to enter on the card with the SIM chip you buy.

There may be simpler ways to get a SIM card for Germany, but I think that this is certainly the cheapest.

BTW, I assume that you have an unlocked phone

I think I have found a good SIM card for calling the US from Germany-- Ortel Mobile, powered by e-plus, (€.09/minute; Connection fee of €.15 a call. Much better than T-Mobile. I was able to get a card on eBay, activated and ready to. I'll top it up when I get there. For more info:
http://www.ortelmobile.de/

Everyone is always so helpful to me that I wanted to share what I found.

Ortel is quite o.k. too. Sometimes, you can even get a pack of 10 for 10€ on ebay or 50 for 20€. Drawback ist the short life before it get deactivated and the connection fee.

There is a promotion from http://www.germansimcard.com
If you use the voucher code "germany" at checkout, you will get a 100% discount on the Fonic SIM-Card.
Since it comes with 20 € airtime credit (by sharing the product on a social network) it's quite a good deal!