I didn't notice this in as being mentioned but I might have missed it...
We have had success with things like estate planning from a local lawyer, tax services/financial planning from CPA's, etc. Basically the higher end services that people think about but either can't afford or don't think about doing....
We have also, in the past, had an airplane flight over the city and have tried before for a balloon ride... hoping to get that this year.
We are also asking each grade level to put together a basket to be auctioned off. To ensure there are no duplicates we assign the basket idea to the grade level and if the teachers decide to change it they just have to let us know in advance. Some of the basket ideas include the local college sports teams (which are big rivals around here), baking/kitchen, football/golf/sports, car care items, etc. This is the first year so we aren't real sure how it will go over but we shall see!
Also, something I haven wanted to try here but have never been able to talk anyone into is an auction for front row parking spots at the mall or wal-mart or somewhere for Black Friday. (Day after Thanksgiving.) Our auction is always in the fall in conjunction with the carnival and I have seen it done in larger cities with larger non-profits... basically a "set" of parking spots right at the door are marked off. The person has to win a drawing/raffle/auction (or something such as that) to be able to park in the section. The section could be 1 spot, it could be 100 spots, depending on what you can get the store to agree to. Then the morning of black Friday, for a certain time frame, which is included in the marketing so they know, the spot is reserved. They can arrive anytime during that time and be assured of the spot. The catch for most I think is the fact that someone has to be at the spot(s) to ensure the right person gets them... great job for a Dad though who doesn't want to go shopping....