Shortcodes for Dashboards?

Hi all -

I have been searching all over with no luck on a few things that seems like they would be simple, but I'm stuck.

Trying to make a custom landing page after log in that gives users options to destination. This landing page would be on our TLD.

1) Link to their own blog (theirname.tld.com) (what I really need is the function to display their subdomain's name, I can code it to work from there)
2) Command to use to display a message on our TLD that is specific to a supporter (vs just logged in)

Thank you so much.

Matt