Here are the top-8 longest words in English... or, more-so in english.
9) Honorificabilitudinitatibus
Letters: 27
Antidisestablishmentarianism
Letters: 28
7) Floccinaucinihilipilification
Letters: 29
6-5) Hippopotomonstrosesquipedalian
Letters: 30
5-6) Pseudopseudohypoparathyroidism
Letters: 30
4) Supercalifragilisticexpialidocious
Letters: 34
3) Pneumonoultramicroscopicsilicovolcanoconiosis
Letters: 45
2) Lopadotemachoselachogaleokranioleipsanodrimhypotrimmatosilphioparaomelitokatakechymenokichlepikossyphophattoperisteralektryonoptekephalliokigklopeleiolagoiosiraiobaphetraganopterygon
Letters: 183
1) Go here to see it:
http://wiki.answers.com/Q/What_is_the_full_chemical_name_of_TitinLetters: 189, 819
I'm not sure how many of these are real. xD