Typically, both editors work out of the box, but if you are using version earlier than those shipped with MacTeX 2011 (TeXShop 2.42) you need to configure engines for ConTeXt manually.
=== TeXshop ===
If you install ConTeXt in your Applications Folder, you have to create a new engine.
Go to : /Users/username/Library/TeXShop/Engines.
Then, create a file with .engine as extension. Paste this in your new engine :
$ #!/bin/bash
$ export PATH=/Applications/ConText/tex/texmf-osx-64/bin:$PATH
$ export TEXMFCACHE=/Applications/ConText/tex/texmf-cache
$ context "$1"
Now, when you will open TeXShop, you can choose this new engine.
=== TeXworks ===
If you install ConTeXt in your Applications Folder, you have to create a new engine.
Go to your preferences inside TeXworks.
In Typesetting Menu, in Processing tools, add a new engine.
In Name, type what you want.
In Program : /Applications/ConText/tex/texmf-osx-64/bin/texmfstart
In Arguments :
*texexec as the first argument
*$fullname as the second argument
*$synctexoption as the third argument.
== Skim (PDF viewer) ==