Returning Multisites a Member Belongs to?

Is there a function or method I could use to call a list of the sites a user is a member of.

I figure there should be a way, since — in sandboxing — whenever I try to have a subscriber access the dashboard it shows an error page with a list of the sites that user belongs to and links for each.

So, does anyone have a clue how I could go about doing this?

Thanks!

-Nick