The Security Mentor

If you get a free account on dslreports.com, you can go to http://www.dslreports.com/secureme_go and have them run a test where they do the electronic equivalent of twisting all the doorknobs to see if they're locked. Don't try this from your work computer without permission.

There's another site that does the same job, http://www.auditymypc.com. They seem eager to sell things. Their spyware removal section made me nervous: it's a list of advertised free products. Unless the owner of auditmypc.com is very careful about who advertises there, there's a risk of one of the crooked phony "antispyware" companies showing up in the results.

Auditmypc.com may show you your "internal IP address", which your firewall should normally hide. They suggest getting their "patch management software" to fix this. I simply changed my browser preferences to stop running Java applets and that took care of it.

In any case, take the results with a grain of salt: there are several ways for this kind of online scanner to come up with wrong answers.