I'm using a secondary L360 for a few specific tasks, one of which is clamav. I figure others can benefit from this. The service is free and I make no guarantees as to uptime, speed, or catching every virus. I will keep it running the latest Debian has to offer (at the time of this writing 0.93~dfsg-1) with freshclam keeping the definitions up to date. If you do opt to use the service for your MTA/Spam/AV solution it behooves you to make sure you fall back to some other form of scanning should it not be available. (This is your responsibility!)
The service is located at snafo-local.atxconsulting.com (which resolves only to a dallas private ip) on port 3310. ClamAV uses separate ports to handle data transfer that are negotiated though the initial connection, the port range my service uses is not the default instead it is 11024 to 12048. Make sure your firewall allows this communication.
Should you have any questions I'm easiest to reach on oftc irc as tjfontaine I also lurk in #linode (where you should be as well)
Donations to subsidize the effort are always welcome
And last but not least thanks to Linode for their spectacular service!