Exactly. That is how I did it. I started off with no idea that the subfield of research I'm interested in actually existed. But I was doing research (see, here's the key: do more research), so I read some papers to boost my knowledge. In browsing through recent issues of some journals (I really like PNAS for general science), a few papers with interesting titles caught my eye, e.g., "The Retrosynthesis of Cute Kittens". So I looked at the author & affiliation list, and Google-stalked each of the authors to find out who the main person (i.e., PI) was (usually they're listed as the corresponding author, but not always). Then I looked at their websites. If their research looked interesting, I bookmarked it, and looked at the website of the department with which they're affiliated, to see if anyone else's research looked interesting. Sometimes faculty will also have links to their collaborator's webpages on their site--I usually check them out too. (And I read the CV's of new professors, to get a sense of where they get their Ph.D.s, i.e., where are the good places to go in the field.) Repeat ad nauseum.
Edit: You'd be surprised at how many names you start recognizing within a few months of doing this ... I sometimes go looking for a paper in, say, Nature, and come across a name I'm familiar with. And I go "hey! I know (about) John Biglab! He's a new hotshot professor at the University of Giants! And he did his Ph.D. with I. M. Prolific at Awesomeness University!" and so on. It's pretty cool.