Each file has an option to be made public. By checking it, you will get a unique URL that you can share with anyone to let them download that file without an account. On your log, the download will be recorded as anonymous.
Groups can also be public. By setting the corresponding option (Privacy -> Public groups and files listings page -> Enable page) you can enable a landing page that can list all public files and groups for easy navigation and sharing, without the need to share specific files URLs. There are also options in the same page to enable the repository for known users only, and to let clients mark their own files as public.