Our elementary school's auction has items that each class donates. For the older kids, the teachers select themes and request that each child brings in either an item to match that theme or money, even $2 or $3. Then the teacher would purchase items with the money. Themed baskets have included movie night, coffee-related, Italian food, summer fun, etc. Some classes have donated only money and then the teacher either makes a "money tree" or purchases lottery tickets.
For the younger classes, personlized items are more popular. For example, one year the kindergarten class got a white apron. They used different color paints, and a teacher (or class mom) helped each child put their handprint on the apron. The adult then wrote the child's name under the handprint. Believe it or not, each year the aprons went for over $500.
Another nice item was a child's bookcase, painted white. The teacher/class mom had each child put a thumbprint on it with different colored paint. Then the mom/teacher wrote their name under it. When the paint was dry, the adult turned each thumbprint into a different animal, for example, a butterfly, elephant, etc. It was adorable and went for a few $100.
My all time favorite was a collection of drawings by a 3rd grade class. One of the moms went into the classroom and had each child draw what they wanted to be when they grew up on a piece of paper about 2"x2" or 3"x3" and write their name on it as well. She then took each picture and had it matted and framed, with a beautiful poem in the middle from a card or something (it wasn't just typed, it was on cardstock and very pretty) about children growing up. It was just beautiful. I wanted it myself, but since I didn't have a child in that class, I didn't bid on it so the parents could have it.
Hope these ideas help someone.
Chris