1) Take a carrier bag and a pair of old gloves with you the next time you walk your dog, or go on a dog-less stroll, and pick up some litter. Today I filled one large bag just by taking a very short walk around the block. Litter is a really big problem on our street and if I can make the street nicer for us all with a small bit of effort then it's a job well done.
2) As someone who has been unwell for a while, which can be very isolating, I understand the importance of having help and company from others. If you've got a friend or family member who is unwell, has had an operation or can't get out and about for any reason, offer to call round to make them a cuppa or some dinner, or ask if they'd like to go for a walk to a local coffee shop. I promise you it will make the world of difference to them.
3) Knock on your neighbours door before you pop out to the shops to see if they need anything.
4) Have a sort out through your wardrobes and cupboards. Take any clothes, books and kitchen bits to your local charity shop and blankets/towels to your local animal rescue centre.
5) Run a bath for your partner/housemate when they get home from a long shift and cook their favourite dinner.