I went through years of this aswell. My kids are now both at Secondary school so I've managed to drop my contact with Primary school (though it did go on after they'd left). One popular stall I always did at the summer fair was The Glass Jar and Bottle Tombola. Collect glass jars with lids (you need to get as many people as possible doing this) then fill them with stuff. I used to put in dried pasta, tea bags, boiled sweets, coloured cotton wool balls, felt tip pens (cheap shops are good for packs of these - just divide a huge pack between a few different sized jars), crayons, pegs (again a big bag of pegs can fill a lot of jars), some of those empty minature jars of jam/marmalade are good, I used to fill one with pennies, and then put 50p in one and �1 in another. Make sure you've got a bottle or two of wine on the table and make it a tombola, but 50p a go and EVERYONE is a winner! The kids used to love it because they always won something. Some of the jars I would fill myself, some of the people who were collecting jars for me would bring one or two filled and then I would write to the nearest supermarket (I also wrote to M&S once who sent me a voucher to spend) explaining what I was doing. If you're lucky they send a voucher to spend in their shop on the things to fill the jars plus buy a bottle or two of wine.
I also used to write to all the tourist attractions in the area asking for tickets. We always got some and then had an envelope stall where you got to choose an envelope, some of them were empty, some had tickets in. I used to write to zoos/amusement parks/cinema/museums - basically anywhere a family would go for a day out.
We also used to have a standard tombola - hook a duck using a paddling pool - coconut shy - ice creams for sale (needs a few cooler boxes) - a bbq (one of the parents made one of those half drum bbqs and we used to sell hot dogs, hamburgers and bacon butties - then we'd have a book stall and a brick a brack