It may be my poor search skills, but I did not find the following. I am adding to hopefully save someone else some time.

How do I get the currently selected language?

The language appears to be stored in a cookie on the client's machine. Try: Request.Cookies("language").Value which returns a string.

I used this for a toggle link that changes between English and Spanish in a module. The Spanish language file sets the link to an Eglish phrase and the English language file has a Spanish phrase. Clicking the link checks the current language and switches to the opposite.

Hope it helps someone seraching "get current language"