"I keep hearing people talking about g++ 2.7.2 (or some other number starting with 2), but the latest version I can find is g++ 1.42. Where is it?"
As of gcc 2.0, C, C++, and Objective-C as well are all combined into a single distribution called gcc. If you get gcc you already have g++. The standard installation procedure for any gcc version 2 compiler will install the C++ compiler as well.
One could argue that we shouldn't even refer to "g++-2.x.y" but it's a convention. It means "the C++ compiler included with gcc-2.x.y."