This is the kind of feature that, in prior iterations of Mac OS X, might have been relegated to the Services submenu, located beneath the application menu (and sometimes available by control-click-invoked contextual menus). It’s always struck me that the functionality available there has been unjustly ignored by virtue of its deprecated location in the user interface; even I rarely remember to access anything available in that submenu, and I generally know what’s available to me and how handy it is.
Above: Look it up. The new Tiger dictionary, not exactly getting it right on the first try, but handy nevertheless.
Tiger’s dictionary is a small step forward for the usability of such system-wide services. It would have been a larger step forward if only Apple had taken some effort to feature it more prominently in their marketing efforts for Mac OS X. The inclusion of such basic reference tools isn’t exactly sexy, but the fact that it isn’t relegated to a single productivity suite, as is the dictionary in Microsoft Office, is a big deal to me. Plus, I know lots of people who could seriously benefit from having more readily available access to a dictionary. Seriously.