I was surprised how much money I can save, by
having the time to think about how to save money
not eating out
not wasting food
not buying things because I have "been working hard, and deserve it"
saving wear and tear on clothes, shoes etc
not needing "smart" clothes for work
no impulse buys, because I have the time to think about what I really need
having the time to repair and/or mend things, and look after things
not buying people presents (and not minding when people do not buy me presents)
also as other people have said, not buying expensive sandwiches etc at work, not contributing to whiprounds, etc.
Especially when travelling by train, taking a flask of coffee.
These may sound small items, but like Dellzegg above they do add up.