A few days ago Fyodor of Nmap fame (yes, that Fyodor) posted to the nmap-hackers mailing list that he was making nmap 4.20 ALPHA 9 available for download on the Nmap download page.
So, why is this important?
In the new 4.20 version Fyodor and Zhao Lei have completely re-written the OS detection engine of Nmap. As a result the new OS detection database only contained 71 OS signatures (at the time of his post), compared to 1684 in the previous version. He's asking for our help in submitting new signatures, when you know what the target machine is. He's also happily accepting corrections when Nmap makes guesses.
Now, we all love and use Nmap, right? Go download the 4.20ALPHA9 and give it a go. This is the perfect opportunity of us to help the project along with new OS detection signatures.
Don't forget to check out all of the other new features as well, and check out the paper/documentation on how the new OS detection works in Nmap.