One thing you have to remember is that your time is slipping into the future.
While it’s a catchy funky song to listen to, it’s also something good to keep in mind. Many people approach volunteering as something they’ll get around to… someday. And someday just never comes.
Just sitting around and being bored is occasionally part of life, but I’d ask you to consider doing something bigger if a friend bails on plans for the weekend or you have a lot of untapped vacation time set aside. Take these unexpected freetimes as an opportunity to give back.
And if your local soup kitchen or animal shelter or library can’t accommodate drop in volunteers, you can always go armed with some gloves and trash bags to a local trail or walk on the grassy verge next to the shoulder of a small (not too busy) road and pick up the litter there.
If you are squeamish about trash you could instead go to a local plot of community land like a small neighborhood park or median in a very low traffic area and help spruce up any neglected plants and mulch there or even add some if it’s a bare patch of dirt. If it’s thoroughly Winter where you live- which it really should be if you live in my hemisphere- you can instead use your time to shovel some neighbor’s driveway or sidewalk if they haven’t gotten around to it yet or if they’re elderly and can’t do it themselves. If there’s some kids in your neighborhood that hire themselves out as shovelers though skip that one and instead shovel a portion of a neighborhood park path or the path to get into the library or some other more public venue to avoid elbowing in on the kiddos’ enterprise to save up for college.