kumarreksituteskenteleentuvaisehkollaismaisekkuudellisenneskenteluttelemattomammuuksissansakaankopahan (102 letters) is the longest word in Finnish.
I'm pretty sure that one of the longest words is hippopotomonstrosesquipedaliophobia It means fear of long words .-.
pneumonoultramicroscopicsilicovolcanoconiosis [noo-muh-noh-uhl-truh-mahy-kruh-skop-ik-sil-i-koh-vol-key-noh-koh-nee-oh-sis, nyoo-] IPA Syllables Word Origin noun 1. an obscure term ostensibly referring to a lung disease caused by silica dust, sometimes cited as one of the longest words in the English language. Taken from dictionary.com