The D-League was an absolute sham before 2006, but they revamped it, put more money into it and did some reorganizing. It's really starting to bear fruit.
However, if you're waiting for a minor league system along the lines that baseball has, it'll never happen, nor should it. Baseball's extensive, far reaching minor league system is really more a function of tradition than anything. Back in the early 1900s, no one had the first darn clue who was going to be good coming out of high school or college, and they'd just bring guys in, let them play and see who came out on top. Scouting is much more sophisticated now, and the need for a big minor league system has probably evaporated, at least from a personnel point of view. But the baseball minor leagues continue to thrive because they're entrenched, profitable, promote the game and because Americans remain suckers for nostalgia.
Pro basketball is different from that: we've got a very well-established college game where teams have a pretty good idea who's going to be good and who isn't. Teams have extensive scouting departments to look at players in Italy, Argentina, Spain, etc. The goal of the minor league is to promote the pro game; if the NBA were to establish an extensive minor league system at this point, that would be putting the cart before the horse.
