Hold an event where people are able to give swabs for the bone marrow register. In the UK we are short of donors. If this could save just one life, then this would be worth it.
People can also order kits themselves from Anthony Nolan or DKMS.
Every 20 minutes, someone in the UK is diagnosed with a blood cancer and some 2,000 people are looking for a potentially lifesaving blood stem cell donor each year. I also know a young boy who has been given months unless a donor can be found.