Free online scanners

Often people are looking for a way to clean up something that their sometimes outdated antivirus can't clean, or another brand of scanner to verify the results of their existing scanner. Here's a list of free, online virus scanners. Most of these will require a small download. It is generally recommended to turn off your existing virus scanner before running any of these. I should also add that these are by no means intended to replace 'installed on your computer' full time, properly licensed and up to date anti-virus software.

To scan entire drives or directories:

http://www.eset.com/onlinescan/
http://www.pandasoftware.com/activescan/com/activescan_principal.htm
http://safety.live.com/site/en-US/center/howsafe.htm
http://www3.ca.com/securityadvisor/virusinfo/scan.aspx
http://support.f-secure.com/enu/home/ols.shtml
http://www.kaspersky.com/virusscanner
http://us.mcafee.com/root/mfs/default.asp
http://security.symantec.com/sscv6/home.asp?langid=ie&venid=sym
http://housecall.trendmicro.com/
http://www.bitdefender.com/scan8/#
http://www.ravantivirus.com/scan/
http://www.freedom.net/viruscenter/index.html

And for single files:
http://virusscan.jotti.org/ (uses multiple scan engines)
http://www.virustotal.com/en/indexf.html (uses multiple scan engines)
http://www.kaspersky.com/scanforvirus.html
http://www.ikarus-software.at/portal/modules.php?name=Content&pa=showpage&pid=4 (send an e-mail with the file attached)