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:

http://www.zanichellibenvenuti.it/wordpress/

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.