Google "word a day." There are tons. I recall some email them to you if you want. Can't give any specific recommendations. I imagine if you can find one by a dictionary it'd be better. Maybe Oxford and such have a "word of the day" email blast? In fact, I think they do.
SFWA.org has a lot of articles about writing. There are others, but it all depends on what kind of stuff you're looking for. If you have any questions, you could post here too and get opinions.