More in the ever morphing world of SQL injection attacks. Sites that were hit with the xiaobaishan.net attack are now directing to flyzhu.9966.org/us/Help.asp and sites previously infected with en-us18.com are now pointing to www.exec51.com/b.js
9966.org appears to be a dynamic DNS service, exec51.com is a fast flux botnet. My best guess is that there are two rival groups performing SQL injections, one of them is Chinese and the other Russian.
The nature of the botnet means that the payload delivery is a bit erratic, but with a bit of effort exec51.com coughs up a reference to fake anti-spyware site advancedxpdefender.com. That tries to install a trojan which is pretty well detected by most AV products.
Thanks also to Amir who pointed us in the direction of his guide to preventing SQL injection attacks - if your server has been hit by one of these exploits, then it might be useful to you.