I did a recent interview that talked a bit about the upcoming Drupal O'Reilly book (code-named the "Lullabook"), how I got my start in the Drupal community, and how I went about surmounting the Drupal learning curve.
The short version is that, in my opinion, getting involved in the community is, hands down, the fastest way to ratchet up your Drupal knowledge. It was the only way I was able to make the leap from "total newbie" (who hadn't even installed Drupal at the time) to "contributing my first module" in 2 very short months (I started out my Drupal career as a Google Summer of Code student back in 2005).
It was a lot of fun to reflect back on my first couple months in the Drupal community, which included some of the following highlights. *cue the flashback wipe*