Sahil Malik has an interesting post about the keeping with the pace of technology. He posted an impressive list of technologies that he manage to get a handle on in a short time.
Frankly, I use a simpler approach for keeping up with technology. I don't. A while ago my company had a guy who dedicate a significant amount of his time to finding out everything there was to know about new and upcoming Microsoft technologies. The end result was that we would get several emails a day, each containing references to multiply resources, from videos to white papers, and everything in the middle. I used to read those emails, just to know what I didn't know, it grew to be a really big list.
My current method of learning stuff is to know just enough about the model upfront, and wait until I have need/wish to use the technology in a real project. To take WCF as an example, it means that about a year and a half ago, I sat in a user group lecture about it, learned that it had something to do with ABC, and left it at that stage ever since. A few weeks ago I needed to know a bit more, so I did. But I won't get into it in any serious capacity until I would have a real need for it.
What this means is that I can talk with some knowledge about a lot of technologies, but that I rely on being able to ramp up knowledge fairly quickly, more than learning up front. I refuse to say: "I do this and that, but not that" (see the tag line), and I just don't see any other option.
The most important thing that you need to understand about new technology is what its model is. This actually mean: "what the mental model that the developers for this technology had in mind". Once you grok that, the rest is mostly implementation details.