We make about £250 on our annual clothes collection. It is easy as it doesn't cost parents anything and all they have to do is bring in a bag of old unwanted clothes/shoes/bedding etc. and to be honest, most of them are glad to get rid of them and bringing them to us when they re coming to nursery anyway is much easier than going to the charity shop. We just send them a couple of reminders by text and put some signs up and then remind them all verbally the last day before collection. The collection date is pre-arranged and they just turn up - take it all away and then send us a cheque - simples! Staff bring theirs in too.
https://bag2school.com/
The other way we raise funds is dress-down Friday - staff pay £1 to come in non-uniform on a Friday (if they want to obviously). We get about £250 per year from that too.
In the past, we have held coffee and cake day for parents - as you say, they are too busy to get involved but if we set up a coffee stall in reception in the morning (we buy paper cups with lids and have an urn set up) and get the cook to make a couple of home made cakes, they will buy a coffee and cake to take to work with them - at £2 a go, its cheaper than Starbucks/Pret et al. and for a much better cause (and many buy extra cake to take for their work colleagues) We also put a couple of tables in the dining area if they don't work and want to buy, then stay and chat with each other (after dropping children off).
Other than that, we have saved money by asking parents to do some jobs for us e.g. weeding, putting shelves up, making cushions/tablecloths/aprons/dolls clothes. Its always worth asking in a newsletter if anyone has any skills we can use.