Quoting from the International Mars Watch Web site:

This apparition the Mars opposition will occur at 18:54 29 January 2010 UT. Mars will have a visual magnitude of -1.28, a size of about 14.1 arcseconds and be about 1.65 AU away from Earth. At opposition, it will be at coordinates (J2000) 08h53m, +22°11' in the constellation of Cancer near the Full Moon. It will appear as a bright red-orange object that should rise at about the same time the sun sets (and set at about the same time as the next sunrise). The season on Mars will be mid spring in the northern hemisphere and mid autumn in the southern hemisphere; LS=44.5° for those familiar with that notation. At opposition, the entire visible disk of Mars is illuminated; it is in its full phase, much like a full moon. Before and after opposition, it will be in a gibbous phase; it can never have a crescent phase since Mars is further away from the Sun than Earth and thus can never be between Earth and the Sun.

Due to the relatively high ellipticity of Mars' orbit, the opposition date will not be the date of closest approch. The closest approach will occur at 03:48 28 January 2010 UT at which point Mars will be only about 61.7 million miles or about 99.3 million km (0.664 AU) away. Although it is closer it will be only slightly, almost imperceptibly, larger and will be the same brightness.

More information here:

http://elvis.rowan.edu/marswatch/opposition.php

Just know that if the Red Planet ever does become as big as the full
phase Moon in our sky, just say buh bye.