"offline" blockchain querying library Is there a library which provides all the same address/transaction querying information as blockchain.info, depending only on having a bitcoind synchronised database?

There are a number of queries which bitcoind cannot answer. For example, bitcoind only indexes transactions which are unspent.

I realize blockchain.info has a public API, but it isn't an option for us to use this. I doubt they'd want us to spider the entire blockchain over their API anyway.
You should take a look at Abe:

Abe: a free block chain browser for Bitcoin-based currencies.

Abe reads the Bitcoin block file, transforms and loads the data into a database, and presents a web interface similar to Bitcoin Block Explorer or Blockchain.io.

Not to mention it was written in Python.