ETA: Sorry, just noticed you're not a kindle user. Have slapped myself with the wet noodle!
Just for fun, I track the daily free e-books thread on amazon.de. It's a mixed bag of self-published finds, but there are a few discoveries now and then...
When/if I find something on amazon.de, I search for it on amazon.com and usually it's free on both sites. Lots of shorter fiction, so that may be useful to you if you're learning.
http://www.amazon.de/forum/kindle/re...TxO14VX15MUAPY
If this link doesn't work, it's: amazon.de/forum/kindle, and the thread title is:
"Aktuell kostenlose deutsche Kindlebuecher"
Usually it's on the first page of the forum