Rapid7′s NeXpose is a vulnerability management tool which scans your network and identifies vulnerabilities across a wide range of devices and operating systems. NeXpose uses one of the world’s largest vulnerabilities databases to identify the vulnerabilities on your network.
And the great news is that there is a free community edition. The NeXpose Community Edition is a free, single-user version of NeXpose and is powered by the same scan engine as its big brother NeXpose Enterprise and offers many of the same features. The single biggest limitation is that it only works with up to 32 IP addresses, but this makes it perfect for small organizations or for individual use.
NeXpose Community Edition is available for MS Windows Server 2003 SP2 / Server 2003 R2 and several flavours of Linux including Red Hat Enterprise Linux 5, Ubuntu and SuSE Linux Enterprise Server. Note: There isn’t an official Windows XP version as XP has some limitations with regards to raw sockets which NeXpose needs to perform its scans.
It is also worth noting that NeXpose Community Edition needs 4 GB of RAM (on 32-bit machines) or 8 GB of RAM (on 64-bit machines), don’t try using it without the minimum amount of memory otherwise your machine will start swapping heavily.
Once installed and updated to includ the latest list of vulnerabilities, NeXpose Community Edition offers a comprehensive range of tools for scanning and reporting the vulnerabilities on your network.
Rapid7 have some useful YouTube tutorials here: http://www.youtube.com/user/NeXposeTutorials