Sticky Tarpits
Something that was brought to my attention was this sticky honeypot that encourages scanning and attacks from the usual nasties of viruses, worms and hackers. This is an open source project called LaBrea. In some ways, it is like an Intrusion Detection System (IDS) that monitors traffic for suspicious activity or even an Intrusion Prevention System. There is even a tutorial on how to install it with irongeek.