Looks like a very useful site, Rat!
This is the site I recommend, to FoLCs and to my students, although I do warn them about the 'serial comma' rule which applies to the US and not to the UK. It's the
Guide to Grammar and Writing site created by Professor Charles Darling.
And, yes, if anyone else has any good ones, let's hear about 'em! You can never have too many grammar guides...
Wendy
(who has three grammar books and a dictionary on her study bookshelf, and another two plus several dictionaries at home!
)