The Virustotal web site is a pretty nice way to scan a file with about 42 different virus scanners. It uses AJAX to dynamically update the results page as the various scanners complete, which can take many seconds. Even better, it feeds sample files to the ClamAV team so they can improve their detection rate.
Recently I have been receiving a lot of trojan spam which ClamAV has not detected. Usually it gets blocked by Spamhaus, but it can bypass that if it gets to me via my postmaster address or via one of my forwarded addresses. I got pretty bored of feeding infected messages to my web browser, especially since it runs on a different computer to my MUA.