If you’re a Mac user who came to OS X from any other Unix (one with a really solid package manager, like apt on Debian GNU/Linux and derivatives), I highly recommend checking out Vagrant.
I’ve really chafed at the lack of decent package management on OS X, and this will likely fill that gap for me. Homebrew is good, but it’s just not as easy as apt. I like using OS X and all the “syntactic sugar” that comes with it, like Netflix Instant and fast Flash, but it’s still hard to do some things, like install LaTeX. If your package manager tells you to go off and download a standalone installer, you know something’s wrong. (I don’t blame Homebrew for this, I believe them when they say building LaTeX from source is hairy, but I still don’t like it.)
Vagrant is a tool for managing virtual machines geared toward web development, but it’s actually more useful than just that. It’s super easy to download a base Ubuntu box and in a few steps have an ssh session into a new virtual machine instance, with shared folders already set up and a command-line interface for suspending, resuming and tearing down the virtual machine.
You have access to all the same packages in the Ubuntu repos without the overhead of a Gnome session running inside VirtualBox. I know you can set this stuff up manually with the VirtualBox GUIs or command-line tools, but Vagrant makes it so easy!
You can install packages directly with apt-get through an ssh session or provision the box with Puppet or Chef, neither of which I had ever used before. Using simple manifest files or “cookbook” scripts would mean you wouldn’t need to worry about the state of the VM, and with careful maintenance of the provisioning scripts, you could trash it and start fresh without a lot of difficulty.
The only tip I have for using Vagrant in this way is that if you’re using Ubuntu, make sure to run “apt-get update” before doing any provisioning, and start the provisioning system with all the verbose and debug options you can enable, because otherwise you might end up with some problem on the apt end but the “vagrant up” command would just hang for several minutes with no output until everything fails and you find out that apt couldn’t find some package lists. At least, that’s what happened to me when I tried to install some LaTeX packages.