As a manager, what would you like the software developers under your management to learn? It might be knowledge of some specific technology/software engineering skill/some other skill or knowledge, or what?
Independent, critical, rigorous thinking. To write well. To think of the next guy. The usual.
Be creative and proactive. Be Slow(not very slow) and have a better solution than being fast with a not very effective solution.
Independent and learn from your past mistakes and most importantly guide the new comers.
I would always want them to revisit the basics. Basics of Programming, basics of Relational databases and keep sharpening their programming and design skills.
Languages dont matter to me much. In my context atleast, the language is pretty much Java. Good developers differentiate themselves in their thought process and problem solving ability. I would like my team members (and myself) to keep improving on these by solving problems and not being complacent after arriving at the first solution.
From a knowledge gathering point of view, I would like them to visit blogs of good authors, participate in TopCoder competitions, be active in technical forums and be well informed about technology in general.