API for downloading block chain data I was looking for an API to download block chain data in real-time so I use the transaction data for analytics.

Is anyone aware of a good API for this?
If you are using the bitcoin-qt client https://en.bitcoin.it/wiki/Bitcoin-Qt, you already have the blockchain in your hard drive (in the /bitcoin folder). The files blk000x.dat (blk0001.dat is the first part, blk0002.dat the second ...) contain all the data. blkindex.dat has the index to the blocks. 

With the command line version, bitcoind, you can check blocks, transactions. The files can also be studied with bitcointools:
https://github.com/gavinandresen/bitcointools

If you are using some other client, the files will be somewhere else, but most likely they will still be there.