It is the 'Friends' at our school. They make a big point of telling every new starters parents and family that everybody is a member of the friends as soon as their child starts school. They have a website linked to the school website that is very useful and successful.
Meeting times are well documented and now take place at the village pub normally to make it more relaxed, the AGM is held at school right after the reception and KS1 start of year meeting, most parents hand around for that as they have wine!
The friends are very very successful at our school as they get the communication about right, website, emails and the odd thing in a bookbag, also the chat at the school gate (made easier being a small village school).
There is an element of them feeling a bit cliquey but I think that's hard to avoid (and no, I am not one of them, in fact shamefaced me has never been to a meeting but I do help out with things when I can), there are lots of fun things organised throughout the school year by the friends, some simply for fund raising like the fate but others are for the parents to have fun (last year it was an adults school disco, this year the theme is the 70's) and also for the children (we have a Christmas craft fair which is fantastic for all including pre-school children and toddlers).
This is a fairly affluent village but there is a really good mix of families from all backgrounds, allot of money gets raised, some split with charities (the three peaks challenge was a good one, half to a charity and the other half built an out door class room and benches for the back field) and some direct for the school.
The type of thing routinely raised by the friends for the school is to buy laptop trolleys (16 laptops per trolley), each class teacher gets £25 per term for incidental class room expenses so the teachers aren't having to put there hands into their own pockets for resources all the time and things like paying the cost of coaches for school trips to keep costs down.
Current things being worked towards are putting in an all weather tennis court and helping to pay for the building of a new classroom so we can have one class per year group.
I think it is important for the PTA to be fun, to be able to see where the time and money goes, to look at supporting charities with things as well and to not put too much pressure on parents to be involved but make it so everyone knows what's going on and why so the load of helping out is shared out so it isn't always the same old people doing everything.
Sorry for the long post!