It seems to me that LtU has many new readers and contributors since moving to the new site. That's great!

Yet it seems to me that the situation right now is that LtU has readers with very different backgrounds, among them many readers who haven't studied PL formally. Others come from academia, and study PL theory for a living.

Since we have such a lively community it occured to me to start a thread for advice on where to begin aimed at those who haven't studied PL theory, yet want to follow the papers and books we discuss.

So the question, mostly directed at old timers, is to which resources would you send a friend asking for advice on learning about the theoretical study of programming languages?

P.S The early LtU archives may be helpful, since I used LtU to organize and collect the papers I read when I began my studies in the field.