I think hacker news can provide you with enough mentions of new languages/ frameworks/ libraries and techniques that you can use it as a starting point for discovery over a long period of time. You can then do your own follow up on the mentions.

It is good for an overview to, lots of other sites and blogs are focusing on say one language or framework.

Well in that case inquiring minds would like to know: How do YOU keep up with technology?

I don't. Then again, I write systems C, so I don't really need to keep up with technology much. If anything, I keep up by reading the emails intel sends me.

This is very domain-specific.

Proggit, OSNews, and Lambda the Ultimate mostly.