Missed edit window:
The Wikipedia entry on Quantum Jump informs me that despite being first released in 1976, and getting some fairly major airplay then, “The Lone Ranger” did not actually chart (reaching number 5) until it was re-released in 1979.
I cannot offhand think of any any examples, but I think it is a fairly safe bet that there have also been some songs mentioning Llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogoch, which is quite a well known British place name, but, of course, it is not quite as long as Taumatawhakatangihangakoauauotamateapokaiwhenuakitanatahu. 
Thank God for copy and paste!
Ah you beat me to it! I listened to this catchy song when I went to Wales and now can never forget how to say that name!
Well, Lemon Demon has, but that’s the whole gimmick in “Word Disassociation”, so I suppose it’s out.
It also uses “paleobotanical” and “skullduggery”, which are words I randomly enjoy, and it presents us with the image of a platypus with a parasol, so I consider its existence a net win for our culture.
It’s spelled “supercalifragilisticexpialidocious,” and in the song it rhymes with “atrocious.”
And backwards it’s “suoicodilaipxecitsiligarfilacrepus” “but that’s going a bit too far, don’t you think?”
I was going to post this song too! I used to have a house in Wales and still the only way I can remember how to say it is by this song. My sister helpfully plays it on the guitar.
Break it down,
It comes around…
Llanfair
pwllgwyngyll
gogerych
wyrndrobwll
llantysilioooooooo
gogogoch!!
ETA: hehehehe “the word that all men fear and dread” - this song still cracks me up!
This has already been topped, but my entry would have been:
“Abcdefghijklmnopqrstuvwxz, it’s the most unusual word I’ve ever seen…”
Sung by Big Bird
And Forbidden Hollywood’s marvelous parody is “Stupidcarelessfictionalnonsensicalverboseness”
Well, here’s a song by someone called Biirdie (sic) that uses the word “uncharacteristically”… at 20 letters, my vote for the longest word used “offhand” (i.e., not in a “look at this funny long word” sense, but just as a regular word).
Queen
Parahumanoidarianised from Machines(Back to Humans)
17 letters:
institutionalized – Suicidal Tendencies, “Institutionalized” (not top 40 US or UK, but Grammy nominated and, IMHO, more relevant than “Broken Silence” – YMMV)
16 letters:
extraterrestrial – Katy Perry, “E.T.” (rhymed with “supernatural”)
15 letters:
unconditionally – Katy Perry, “Unconditionally” (maybe the longest word in a Top 40 title?)
intellectualism – Sheryl Crow, “Everyday is a Winding Road”
revolutionaries – Coldplay, “Viva la Vida”
I don’t recognize that one - can you hum a few bars?
I love it! It’s like Sean Bean.
Yes: Ice-T “First Impression”, from his album O.G.: Original Gangster.
However, it’s a spoken-word track (in the context of a fictional interview) so that probably doesn’t count.