Hard drive data destruction

I have been using Darik's Boot and Nuke on hard drives to irretreivable destroy data stored on them.

If I wanted to check to see whether any data on those drives could be recovered with commonly available tools, would would be the best way to look? I used to have a tool or two for finding deleted files and such, but it's been a while. Any good recomendations on something I can use to see just how gone that data is before giving those drive to other people, or selling them alone or as part of computers?

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EDIT:

Well, maybe this answers my questions.

http://users.telenet.be/mydotcom/howto/data/dbantest.htm