I can’t believe I haven’t linked this yet, but I guess I ran across it before I started the blog. Anyway, Jeff Miller’s A Collection of Word Oddities and Trivia is your one-stop shop for, well, word oddities and trivia. Want to know which seven-letter words can be played on a musical instrument? The world’s longest acronym? Some common words which change from one to three syllables upon the addition of just one letter? Sixteen spellings for Hanukkah? Those and many more are on page 1, and there are 19 pages (three of them containing “long words”). The level of obsessiveness can be judged by this bracketed note on page 11:
[Note: To be precisely correct, pneumonoultramicroscopicsilicovolcanoconiosis is the longest vocabulary entry in any English-language dictionary. Stuart Kidd points out that a longer word actually appears in the OED2, although only as part of a quoted citation for a different word. It is a 75-letter chemical name with numerous hyphens, and it is described on page 13 of this web site. Several other citations in the OED2 include multiple words that are "run together" with or without hyphens, forming "words" of more than 45 letters.]
And these are long pages. Abandon all hope of getting anything productive done in the near future, ye who enter there!
(I was reminded of the site by an Ask MetaFilter question.)