If you want to allow reuse of your open content as widely as possible, with attribution, the options are:
- Public domain: you give up all rights including attribution.
- CC-BY: this requires attribution, but doesn't give the ShareAlike protection against it being used, modified and copyrighted. If someone modifies it and doesn't share back, you can't freely use the adapted work).
- Dual license of CC-BY-SA and CC-BY-NC-SA. Note: This is the most complex option, and you need to word your permissions statement carefully. If at all unclear, then a simple CC-BY-SA is probably the wiser option. This option means that blogs or other sites using CC-BY-NC-SA can use your work - however you still can't use theirs if (for example) your site is commercial, or otherwise conflicts with [the conditions of the noncommercial clause]. If you want to be able to freely use content from other sites (other than only public domain or CC-BY), you will need to specify CC-BY-SA as your primary license, and say on your license page that all original content on the site is under both licenses, but if any CC-BY-SA content is used in a post, then that content is under the CC-BY-SA license only.