It's National Grammar Day and I have a couple of links. Disclosure: My blog is listed on both sites which is how I found them. I think it has something to do with that Encarta review I did and I've been getting hits. Regardless, they still offer some neat stuff.
SPOGG is the blog fo the Society for the Promotion of Godo Grammar and it's a really good read with lots of great examples of bad grammar. I may stick that one in my sidebar.
Here is the site for National Grammar Day and if you look through it you can find lots of useful links and even a download or two to help with grammar.