Condensed from here: https://support.google.com/a/answer/2589954?hl=en:
- google.com
- googledrive.com
- google-analytics.com
- googleapis.com
- googleusercontent.com
- ytimg.com
- gstatic.com
The above are all on port 443, HTTPS, only. There is a legacy product which uses talk.google.com on port 5222, XMPP.