Microsoft Security Analyzer

http://www.microsoft.com/technet/security/tools/mbsa2/default.mspx

This is a good tool to scan systems remotely for security issues.

The checks that are of interest:
1. Security Patches
2. Weak passwords
3. Firewall running

Here are the pros & cons

Pros:
1. Can scan multiple systems
2. Does several good security checks
3. Easy to use GUI

Cons:
1. No command line
2. No plain-text/CSV report option