Is there a dictionary where the frequency of a word appears?

Question

Not so recently somebody posted a link to a dictionary that displays the frequency of a word. Well, I just forgot its name.

Of course there exists Duden, which however classifies words only in six possible levels of use. That dictionary I saw gives a better output and and takes as reference the word der (I don't say the 'article der', because I'm not sure they take the word as only meaning the article). Hence the output has, among otheres, the line:

<Input word>. Index: 6

and that means, <Input word> is used about 2^–6=1/64 times as often as der.

Could somebody refresh my memory?

Answer 1

Here is an online-tool where you can enter a word and get its frequency-class together with lots of other interesting information:
http://wortschatz.uni-leipzig.de/abfrage/

Here is a list of the 10,000 most frequent german words:
http://www.udel.edu/LLL/language/deutsch/top10000.pdf

Here you find links to similar lists for the top 10, top 100, top 1000 and top 10,000:
http://wortschatz.uni-leipzig.de/html/wliste.html

And here you find a list that is made from the DeReKo (deutscher Referent-Korpus = german reference corpus):
http://www1.ids-mannheim.de/kl/projekte/methoden/derewo.html