[grumps]

I think that completely depends on your goals. Are you wanting to work for a startup company? Are you thinking an agency? freelance? Or are you thinking some large corporations? The answers will vary slightly, IMHO.

If you're thinking Agency/Freelance, I'd look at agencies that you'd like to work for. Check out any blog posts from the tech team, or current openings. Sometimes there's little tidbits in there if they're shifting tech directions.

If you're wanting to work for a startup, I'd suggest looking in the startups in your current location. They're may or may not be a correlation to the technology that's being used.

If you want to work for a corporation, you would probably be best to learn .NET/Java. I know that's going to annoy someone but for the most part companies want .NET.

You could also base in on the who's hiring trends if that's your goal.[1]

If you want to learn for heck of it, pick a technology that seems to draw you.

[1] http://www.ryan-williams.net/hacker-news-hiring-trends/