Personally, I don't donate tinned soup, baked beans, tinned tomatoes and dried pasta because I sort the proceeds of several harvest festivals (for a charity for whom I volunteer) and there is always loads of this stuff. At my DD's school, the lady from the food bank giving a talk to the children about it asked them, if possible, not to bring in baked beans because they had more than enough too.
I would donate UHT milk, long life juice, tinned meat and fish, tinned meals such as beef stew, chicken curry although be wary of things like Fray Bentos pies as they take a long time to cook, and people don't always have access to an oven, or can't afford to run it for long periods of time. Tinned fruit and veg are always welcome, tinned custard, rice pudding. Since my DD went veggie, I always try to put in a tin of macaroni cheese or vegetable curry too.
Treats such as biscuits or sweets/chocolate are also always welcome. If you are going to put in advent calendars (which I think is a good idea!), please do it asap so that there is enough time for them to get from the collection point to where the parcels are made up.