There are plenty of "word a day" offerings out there (I think my screen saver even has one) but most of them assume you have a pretty basic vocabulary and they are formatted like basic dictionary entries: dry, dry, dry.
A while ago I subscribed to Wordsmith.org's A.Word.A.Day e-mail and it has been such a pleasure--each week the words are grouped around a theme: sometimes it is the connection to a particular language, sometimes the words are derived from birds, sometimes the words are esoteric insults (always good to have some of these tucked away so I can swear in front of the critters without major repercussions). This week's theme is "words with three letters in alphabetic sequence." (You can browse the theme list here.)
Today's entry was simply perfect: defenestrate*. The former-French-speaker in me could figure out what it meant by the connection to the word window: "fenetre". The basic pronunciation, definition and etymology are covered, but the notes section, in which the word is explicated and commented upon, is what makes A.Word.A.Day special. In defenestrate's note there is a reference to the Defenestration of Prague which took place May 23, 1618 and led up to the 30 years war, but then, even better, there is a link to a Lego sculpture gallery of this particular historical moment! If I was a kid studying for the SATs you can bet I would remember defenestrate after looking at the Lego pics.
I love obsessive dweebitude things like this. Do you have a favorite to share?
*Incidentally, Blogger's spell checker does not know the word defenestrate. Ha!