This looks pretty good - does anyone know of any others?
http://grammatica-italiana.dossier.net/grammatica-italiana-02.htm
I don't know if these are any better, but here they are:
http://www.grammatica-italiana.it/
http://www.grammaticaitaliana.eu/
This next one is not a systematic grammar, but it's very nice for deepening your knowledge about selected topics:
If I were you, I would just stick with the guide in the link you provided. It is accurate, unlike many other sources on the internet.
I think this one is going to be the best for you: http://www.mmdtkw.org/ItalGram.html because you can find the explanations in English language. I don't know what is your Italian level, but for the begining, it's not bad.
Good luck with your studies.