All sites that are not actual Q/A sites are not listed.
- SE Chat
- SE Data Explorer - Often referred to as SEDE
- SE Dev 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.
- SO Blog Alternative - Why two...
- Stack Overflow "Facebook" tag - Redirects to SO with a truckload of
facebooktags) - Stack Overflow Jobs - Redirects to SO Talent
- Stack Overflow Careers - Redirects to SO Talent
- Stack Overflow Talent - ↑↑↑
- RADS - Used to be a dedicated redirection site. Closed now (redirects to SO)
- SO Developer Console - Not a test site!!
- DevDays - This is discontinued.
- SO Email Host???