Is there a lightweight blockchain parser library/server?
There are a couple available:

https://github.com/znort987/blockparser
Which is c++ based and has some basic analysis functions already written.

http://codesuppository.blogspot.com/2014/01/how-to-parse-bitcoin-blockchain.html
describes the basics of parsing the block chain and links to code written by the author of the post.

It looks like most projects don't parse it directly and use the RPC interface of the main bitcoin client.