SAT Prep Tools -- Grammar

I know that grammar can be difficult to understand. Here are two resources I've found that have been a great help to me.
This automated sentence diagrammer has helped immensely as I write the grammar-related posts on this blog. Simply type in a sentence, and it generates a diagram for you. Then, when you point your cursor at a word, it displays the word, its part of speech, and its function in the sentence. The downsides: On complicated sentences, it often generates multiple diagram or gives an error message ("Could not find an utterance.") Sometimes that error message means that there is a problem in your sentence, but sometimes it just means that the sentence is too long. Also, there is a one-time (free) download before you get started. Just follow the prompts and you should be fine.
The author of this blog reviews grant proposals and other formal writing, mostly in the medical field. Occasionally some topics will crop up that are specific to that field and not to other formal writing, but almost everything posted here is relevant to formal writing in general and, therefore, to the SAT. This is a great place to internalize what correct English looks like and sounds like so that your writing can improve. A grammar blog might seem dry, but the posts and explanations are clear and well-written, and easy to follow. The downsides: It doesn't have a "subscribe by email" field, but it does have an RSS feed to which you can subscribe. I set mine up in a widget on my iGoogle page, but I don't always remember to check it. It will take some discipline to remember and keep up with the blog.