A few suggestions:
Smile! It will make you feel better and everyone around you feel better.
For your neighborhood:
Go for a walk, take a sack and some gloves and pick up trash.
For the earth:
Use a reusable mug when getting your coffee fix for the day and choose an organic, fair trade, shade grown coffee.
For a stranger:
If someone has less items than you at the grocery store, offer to let them check out before you.
Don't harass them. Keep dogs on leash or under voice command at all times, keep cats indoors or put a small bell on their collars and teach the children in your life to look, admire and respect the wild creatures around them.
Do one of the tasks or chores that you know is a family members least favorite.
For your neighbors dogs:
Put a bowl of water out near your home for those walking their dogs. Even better- pick up some healthy organic dog treats and place them in a waterproof container with a sign explaining that they are there for the doggies to enjoy.
For yourself: Choose healthy and tasty options for your meals and take the time to just eat and enjoy the food.
Lots more information and ideas can be found here:
and for online random acts of kindness:
There's a great article about it here:
Let's spread Kindness!