These are some others that I have collected over the years:

Single file scan:
http://www.gietl.com/test-clamav/
http://old.antivir.ru/english/www_av/
http://www.kaspersky.com/remoteviruschk.html
http://sandbox.norman.no/live_4.html
http://www.unasoft.com.ua/eng/online.html

Whole system scan:
http://www.emsisoft.com/en/software/ax/
http://www.ewido.net/en/onlinescan/
http://www.windowsecurity.com/trojanscan/
http://uk.trendmicro-europe.com/cons...all_launch.php <--- this works with Firefox
http://www.tenebril.com/scanner/main_scan.php