http://bitforce5.com/ shows the transactions as they stream from
http://blockchain.info/. They appear in a D3 force-directed graph with nodes for transactions, addresses, blocks, and IP addresses. It links the transactions to input addresses (red) and output addresses (green) which are sized relative to their amount. Some interesting patterns appear. Should a block be mined, it connects to any related transactions. There are special buttons that track the top 10 output addresses or known gambling addresses. You can also drag-hold-drop nodes to stick them in place. Double-click a node for blockchain.info page. Click and drag over links to cut them. It also has sounds relative to transaction size. My next move will be to improve GEOIP, to use countries rather than specific IP addresses.
It works best with Chrome, but FF works OK too. Since the code is all in javascript, you're welcome to read (plenty of comments and not minified).
Feedback and ideas are welcome!