If you're in the market for a word-a-day/word-of-the day email list, let me recommend the two that I get. First off, nobody seems to do it better than yourdictionary.com. Sign up for the list here or simply click the "register" link at the top of any yourdictionary page. I haven't been able to get into archives lately, so that's a shame. But if they fix that page it's a must visit. Exhaustive yet still captivating info on many searchable words.

GopherCentral offers free lists on a variety of subjects. To sign up for their WOD list, go here (it's at the very bottom of the page of offerings). They also have archives.

Note: As long as we're talking about yourdictionary.com, I might add that this is a great site to explore if you haven't already. This is a great page of references, and they even offer gobs of free language learning materials gathered from around the web