Let me clarify my post from earlier:
If day-to-day erasing and secure movement of files and directories is what you are looking for, then
eraser is what you are looking for.
To literally nuke an entire disk,
DBAN is a good choice. The only gotcha is that the open-source DBAN does not have any of the certifications that many regulatory bodies are looking for (there exists an enterprise version that you pay for that does come with these certifications.
So, eraser=moving/securely wiping files on a running OS.
DBAN=remove all traces of everything (including the OS) from a particular disk.