i might just start a series... things-to-keep-in-jars. here are two more.
just peel some garlics, wash and dry them. then toss them in a clean and dry jar and cover with olive oil. this is a great way to conserve your garlic for longer and you end up with a really fragrant olive oil. you can also add some dried herbs, like oregano, for instance. if it's too hot, you can put the jar in the fridge, taking in account that the olive oil will become solid. that's no problem.
good old apple sauce to have as is or with yogurt and some cereal or even in cake recipes and such.