Post your favorite appliances or "all-in-one" programs. Whether it runs in a virtual machine, or on its own hardware, it all goes.
My submission is Untangle. It's an open source network gateway (their term). Essentially, it can run a plethora of things that you may otherwise end up buying another appliance for:
- Web filtering
- mail spam filtering
- phishing monitor
- spyware blocking
You name it, it's all there. Best of all, it's mostly free. A few appliances have annual costs due to inherent licensing or subscription costs. If you are looking for a new network perimeter device, definitely check it out.
The underlying OS doesn't matter, because it's the application we want to praise, not the OS beneath it.