Mac: It's easy enough to use a system service to launch Terminal from any folder in OS X, but you don't have much in the way of options. TermHere does the same thing, but allows you to pick your Terminal app of choice, and even open multiple directories.
Once TermHere is installed, you can right-click a folder in Finder to get a "New Terminal Here" option. Click that, and Terminal will open up in that folder. That itself is already built into a Mac's system services menu. TermHere adds the ability to pick your Terminal app of choice, like iTerm, as well as set it to open multiple directories in multiple tabs. If you use a third-party Terminal app, TermHere's a great addition to the right-click menu.
TermHere (Free) [Mac App Store]