I'm interested in finding a cloud service that I can share documents with other people. Most allow this feature, but often these other people are required to create an account in order to view/update documents. I essentially want to find a service that allows me to create public storage. A simple "guest username" and password would work as well as an entry point, but I do not want my shared guests to be obligated to creating a new account. Are there any services that allow this feature?

You can use a FTP service and it would give you what you want. FTP - File Transfer Protocall.