TeXShop is a TeX previewer for Mac OS X, written in Cocoa. Since pdf is a native file format on OS X, TeXShop uses "pdftex" and "pdflatex" rather than "tex" and "latex" to typeset; these programs in the standard teTeX distribution of TeX produce pdf output instead of dvi output.
MarcoPolo brings context-aware computing to your portable Mac computer. It allows your computer to determine its context through gathering evidence from your environment (evidence sources), using flexible rule-based fuzzy matching to make an educated guess (rules), and then performing arbitrary actions upon changing context (actions). MarcoPolo's concept of contexts is a generalisation of a location, and encompasses more than just where your computer is. A context might represent what you are doing, or what else is going on around you. MarcoPolo quietly stays in the status bar at the top of your screen (right-hand side of the menu bar), from where it can be configured to your own needs.