I love 当て字（あてじ）, the compounds made up to reproduce the sound and/or meaning of a foreign word (and sometimes of Japanese words too). They were used before カタカナ started to get popular.
Here are some cool examples:
珈琲（コーヒー）
型録（カタログ）
寿司（すし）
倶楽部（クラブ）
煙草（タバコ）

倶楽部 and 型録 are two of those that match both meaning and pronunciation of the loan word. Awesome!
(煙草 simply ignores the normal readings of its kanji)

EDIT: source: http://ja.wikipedia.org/wiki/当て字, and the english version of the article too.

Last edited by nac_est (2008 June 15, 5:35 am)

I've found a new cool word:再従兄弟, "second cousin".
従兄弟（いとこ, cousin）is quite common and it's a nice compound, but 再従兄弟（はとこ） is the only word I know that has more kanji than syllables... how cool is that?
It can also be written as 再従姉妹, depending on the sex.

放物線 means parabola, in the mathematical sense. I like how the kanji are related to the physical aspect of the word: it's the line travelled by a "thing" when you let it go, due to gravity.