Damson jam is fabulous though quite strong in flavour. Very tasty in the middle of a chocolate cake!
My mum doesn't take the stones out, but I think removing the stones is a faff but much easier to eat the jam.
My jam keeps very well - especially if you use the paraffin sealing method.
It is also fabulous if you cut the damsons in half and spread on a piece of puff pastry - little bit of sugar and in the oven. Yum with crème fraiche. Spiced plum chutney would also work on this one.
Stewed fruit in the freezer is pretty good too. Again, it is a strong flavour, so you might want to mix in with some apple.
Have fun! Maybe get a good film going for the de-stoning!