How to do \"sudo apt-get install \" on OSX?
Others have mentioned MacPorts and Homebrew; it might be worth noting the difference between them.
MacPorts works for me, happily enough. But it has the very annoying feature that it wants to install everything. Thus on several occasions, I've had to drag it back from trying to install its own version of Perl, ignoring the system one, or TeX, and even gcc. Now, the reason for this is, I imagine, that if it were to rely on the system versions of these (or any preinstalled one in the case of TeX), there might be some version-skew issue that would cause something to break. And disk space is cheap. That's probably true, sort of, but it still seems a bit obsessive (and I'm not sure I want to use anything that's quite so dependent on specific versions). Sensible or not, it sets my teeth on edge every time it happens.
Homebrew, in contrast, specifically aims not to duplicate tools that are already installed. When MacPorts does its install-the-world thing, I usually end up killing it and installing the package with the mad dependencies by hand, so I've never quite been driven to the point of using Homebrew, but I've been on the point of doing so, ever since I first heard about it.