Floccinaucinihilipilification means rare, the estimation of something as valueless. By the way, the picture is a grab from the movie Bad Words, highly recommended!
While writing this blogpost, I was intrigued by the topic, and so I did a little digging around. Here are some amazing things I uncovered. Well, didn't take all that long - with Google :)
The longest word beats floccinaucinihilipilification by 189,790 letters, and it is the chemical name for titin, the largest protein. Obviously, you won't see this in any dictionary, and hence is disputed as a word. I won't even bother trying to write it here, because I am very particular about spellings, and don't want to get it wrong LOL
Pneumonoultramicroscopicsilicovolcanoconiosis is the longest word to appear in a dictionary, at 45 letters, and it seems to be some kind of lung disease.
Honorificabilitudinitatibus is the longest to appear in Shakespeare's works, and interestingly, has alternating vowels and consonants.
And just for the record, if you ever reach Llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogoch, remember, you have reached a Welsh village in Britain.
For more details and digging around, check http://en.wikipedia.org/wiki/Longest_word_in_English or try your luck on Google.