When I retooled myself from a physics dropout to a programmer (back in the 80s) the most valuable single thing I did was to work through SICP, doing most of the

When I retooled myself from a physics dropout to a programmer (back in the 80s) the most valuable single thing I did was to work through SICP, doing most of the exercises plus little projects sparked off it. (I already had years of hobby programming experience, though; and I'd hope there's a better most valuable thing now, 20 years later.)