When my students were practicing writing business letters I compiled the names and addresses of popular business/companies that my students could write actual letters to. This was a great activity and my kids were excited to see if the companies would write back to them. Some of them received letters back and even got some awesome swag (mostly stickers haha).
The companies included are:
All the companies are set up on one page so it's easy to print and students have all the choices in front of them.