All sites that are not actual Q/A sites are not listed.
- SE Chat
- SE Data Explorer
- Development Test site
- A few redirector sites
Strictly speaking, Area 51 is not in the list, but it's easily known and accessible (it's in the top-left dropdown menu of all sites, though).
Sub-domains of StackOverflow.com:
- Stack Overflow Blog - This isn't really a sub-domain of stackexchange.com, but since SO is a part of the SEN, let it be here. And it even has an Alternative. Why two...
- Stack Overflow "Facebook" tag - Redirects to SO with tag
facebook) - Stack Overflow Jobs - Redirects to SO Talent
- RADS - Used to be a dedicated redirection site. Closed now (redirects to SO)
Other primary domains that the Stack Exchange company owns:
- Stack Snippet - Host site for code snippets in Stack Exchange
- Stack Snippets - Jeff Atwood may have smashed a giant S on this domain. Makes no difference from the above one
- Stack Promos
- SO Business