Texniscope is a beautifull DVI (and PDF) viewer. It is free and well integrated with MacOS X.
I needed such an application. In the X11 world there is plenty of dvi previewers (xdvi, kdvi), but for the MacOS there were none, a part from MacDVI, shareware and ported from the old MacOS (and less user-friedly than its X11 counterparts).
Texniscope also support source specials, you can have a read at my post here.