best german learning website

The Goethe Institut is very good and it has a distance learning program. The result of their tests are also recognized formally from the German State. So if you achieve a certificate with them, it will be valid for anything you would like to do in Germany.
And besides all, it's very high standard. The classes (I do not know about the distance learning program) are quite expensive, but you will get a lot from your money. Usually they cover program faster and more efficiently than any other language institute I have seen in Germany.

I'm moving to Germany in October and I'm just learning the language now. I'm using Rosetta Stone and it is great! Expensive but very good!

I like to use the Deutsche Welle website. It is free and I think very effective. I believe the BBC might also have one too, but you really should check out Deutsche Welle. YOu can be an absolute beginner to more advanced and use it!

deutschkurse.dw.de/KursPlattform/WebObjects/KursPlattform.woa/wo/2.1

couchteacher.com
You can choose a German teacher for yourself.