Ultimate Boot CD (UBCD) includes things such as Parted Magic and, if you're happy to use something that does not have (does not need) a windowed GUI: HDAT2.
If you want to securely erase free space whilst running Windows, I recommend Eraser.
For Windows, I know easeus partition master can wipe all your data on the hard drive or wipe the free space only. For Mac, Drive Genius do the same thing.