Plenty of usage books warn writers to avoid confusing imminent and eminent. Imminent means impending (as in "imminent danger") and eminent means prominent (as in "an eminent author"). Easy enough, although it's worth noting that eminent has been a variant spelling for imminent in the past, though it's now regarded as an error.

Then there's immanent. The Unabridged Dictionary still lists imminent as a variant spelling of immanent (and the OED includes several examples), but today it's safest to regard them as different words. Immanent means inherent, as in this sentence from an article by Anthony Burgess: "beauty is not something imposed but something immanent." Here's a sentence using both words from Arthur M. Schlesinger, Jr.'s The Theory of America: "The Kingdom of God was deemed both imminent in time and immanent in America."

Immanent is more likely to be found in philosophical or scholarly writing than in ordinary discourse, but, since the spellings are so similar, be careful to keep the two words distinct so as not to confuse readers.