Panda has released a public beta of their cloud-based antivirus recently. Its currently being distributed free of charge, it uses a lightweight AV that is based on the PC of the user and in turn connects to the company's cloud-based servers.
It requires only about 17MB of RAM, which makes it compatible with much older machines. The cloud servers scans the PC of the user which collects the malware data and runs it against its database, unrecgonized or new malware are in turn identified and classified to keep the system upto date with threats to end users. The initial goal of the company is to clear the malware problem on the users end which would then enhance ther experience.