From the navel-gazing department of legitimacy: The Oxford Dictionaries Online has added the term "lifehack" to "the world's most trusted dictionary". Their definition:
lifehack: a strategy or technique adopted in order to manage one's time and daily activities in a more efficient way
If we're getting picky, we'd prefer it as "life hack", but it's hard to quibble when we're so pleased. For more advanced reading on the term coined in this talk by the father of life hacks Danny O'Brien, check out our interview with O'Brien and take a gander at the life hack Wikipedia page.