From Panda:

After 7 months in beta testing, Panda Cloud Antivirus 1.0 FREE Edition is finally available. You can download it from http://www.cloudantivirus.com.

In version 1.0 we have improved most of the issues submitted during the testing period. Some of the improvements it incorporates are:

- Supports Windows Vista and Windows 7 64bits.

- Ability to restore any neutralized file.

- Improved detection & protection against rootkits.

- Free Technical Support forums.

Remember that Panda Cloud Antivirus 1.0 is 100% FREE for home users and non-profit organizations and schools. In adition, you can install it in multiple PCs.

So it's available in a 64-bit version now, which is nice (and necessary). I happen to prefer Microsoft Security Essentials, but I found Panda Cloud Antivirus to be effective and lightweight, which is pretty much all you can ask of a Windows AV product.