Sites for searching the blockchain? This is a general question, but what's the best way to search the blockchain? Blockchain.info lets you search by address, but it seems to be a side feature instead of its central purpose.

Are there other sites for searching Bitcoin transactions? I want to see all the transactions associated with a single address or to do other arbitrary types of searches?
The term for such a site is block explorer and there are many of them.  Among the top Google hits for "block explorer" are:


http://blockexplorer.com
http://blockchain.info
http://biteasy.com
http://blocktrail.com
http://btc.blockr.io
http://bkchain.org