If you spot a stranger trying on clothes alone in the changing room, and something looks good on them, tell them. Especially if they don't look sure.
If you use the last of the toilet roll, find a way to replace it so the next person isn't caught out.
Create personal vouchers for friends and family to cash in when they need you to do something. For example, chores, babysitting, DIY, etc. Or, if you are feeling extravagant, for something further afield like a day trip.
Donate unwanted books to your local library - even if they can't put them on the shelves, they can sell them to raise money.
If someone you love is going on a trip hide a note or a little reminder of home for them to find in their case while they are away.