Ask HN: How do you learn a web framework?

Hi.

I've been disconnected from "web development" for sometime since I don't do it at work. I once used Rails pretty well (pre 2.0), but now I find I'm out of touch and Rails too bloated (as a framework) and slow (due to Ruby?). Perhaps, it is also more expensive to run experimental sites on than, say, Django).

I frequently have ideas which I want to experiment with, and know should take less than a weekend to hack together with one of the newer frameworks/libraries.

So, two questions: first, what are the best frameworks to get a prototype as fast as possible. Scalability is not a major issue for now: I think if an idea's good, it will still be used if it's slow/unreliable (e.g. early Twitter), and one can scale in the meanwhile.

Second, how does one learn enough to hack something quickly together in the framework you suggest? I've seen "Getting started" tutorials are frequently insufficient for real work, but books are too tedious (old examples: Rails screen-cast and the Pragmatic book). Is there a middle-ground for your framework?