A couple of interesting sites for grammar geeks (and let's face it, if you're a poet, you should be a grammar geek--even, and perhaps especially, if you like to break the rules, you should know what they are first).
Anyway, the first is from the Language Log, an interesting site I recently stumbled upon. Lots of interesting posts in the archives, including a statistical look at one of those silly rules of the English language: "i" before "e" except after "c". Don't let the statistics scare you off; it's surprisingly readable (and actually kind of funny, in a grammar-geek sort of way).
The other is yet another podcast and website (lately I've been thinking I should change the name of this blog to Poetry and Poets in Podcasts): Grammar Girl. Much of what you hear in the podcast is transcribed on the website, but the podcast is quick and painless (or, as Grammar Girl likes to say, "quick and dirty"). The podcasts usually run four to five minutes, so they don't tire your patience, and Grammar Girl has a nice, laid back attitude towards grammar, a refreshing change for a subject that tends to have almost as polarizing an effect as religion. She also talks about both British and American usage, which is refreshing too. I must say that she has cleared up a couple of nagging questions for me (quick, what's the difference between "toward" and "towards"?). Plus there are lots of links and references at the end of each transcript on the site. I highly recommend it.