I like that Parakeet - I never really put it into that perspective before.
For me, assuming you get rid of any religious overtones to the word "sin", sin is basically anything immoral. I don't believe morals stem solely from religion but rather from society as a whole and personal beliefs in general. Of course religion plays a large role in the society you live in, but general humanity plays a larger role. To me, societal morals were worked into religion, rather than the other way around.
For example, a few hundred years ago, it was considered moral to kill a scientist for blasphemy against god.. Societies outlook has changed, and therefore religion has been altered in the process.
As for specifics, your general: murder, adultery, rape, etc... all of which could go under stealing if you look at it in Parakeet's frame of mind.