There is waaayyy more to android apps than Google's market offers up.
Plenty of other sources. If you do web searches for specific apk files you'll find some of them. I get my apps from Amazon's appstore, Freewarelovers, SlideME, or just floating around.
As for Sony Reader for android:
http://thetechjournal.com/electronic...-devices.xhtml
http://goodereader.com/blog/uploads/...e.reader-1.apk
I understand some folks are not too fond of this particular blog but it has its uses.
http://goodereader.com/blog/electron...our-tablet-pc/