Is there a shop like Cydia on iOS for Android?
While there are Android markets offering pirated versions, (not try before you buy which is signified usually by Demo or Lite) as the other users have mentioned, installing them is very risky. I would recommend being involved in the development community. As a developer I share keys and am invited to test apps often by frequenting XDA forums and Reddit.com/r/Android. 
Developers will discount or give away versions of their apps and being involved in the community will help you learn more and score you some software deals.

Update:This answer does not really address the question.