My third tool is ready to go!
FavorSaverThis tool allows you to dig through your inventory and select items that you'd like to donate. It then helps you compute the amount of favor you can generate, and lets you set goals. The intent is to let you see how the items you have can help you reach specific favor targets, hopefully without exceeding them (and therefore wasting favor!)
Oh, and also since it's come up twice - the API methods don't allow me to access your current favor per giant and/or your XP/favor caps for the day. It's not information they're currently providing. I think it's been requested, but I'll go and throw my hat in the ring as wanting it as well.
Now that we've calculated the formula for XP from donations, I've added that to the tool. Cap information is still not something I can reliably calculate from the API, so that's going to have to wait...