iPhone Hacks is used to describe any iPhone downloads, unlocks and tutorials that are intended to open the iPhone device to achieve what Apple "never intended", like connecting an external keyboard to the iPhone, record full-motion video, or remotely access your home network to control a desktop computer. Using the word Hacks is a misleading if you think the term means something illegal, as iPhone Hacks do conform to Apple's guidelines and doesn't risk breaking the warranty.
See also "iPhone Hacks Group Sees 3.0 Bonanza" on internetnews.com.
See also "iPhone and iPhone 3G b . What's The Difference?" in Webopedia's Did You Know...? section.