existing websites are a good resource for ideas on what is a good source of information to have on a website.
Many PTO websites are at
dmoz.org/Society/Organizations/Education/PTA/
but you will need to do a search on PTO in order to look at the PTO sites.
Many of the PTA sites will stil be good to look at - since the information that parents are looks for - whether it be at within a PTO organization or a PTA organization - is still the same information basically.
Events, Board members, calendar dates, locationa and times, fundraiser updates (who's in charge, contact infomation, deadlines for turning form in and sending money in), etc etc.
Just start exploring other sites, make notes of what you think is informative and what you think would serve the families with information - think of your website like you would your newsletter - since most of the information in the newsletter is upcoming, current or past news and they would look to the website for the current stuff.
That's my two cents - I keep the fluf low - and the information high on the priority list.