Next Monday, 24 December (Christmas Eve), Mars (seen here in a composite image taken by the Mars Reconnaissance Orbiter last week) will be in opposition with relation to Earth; what this means it that the Sun, Earth and Mars will be in a straight line and Mars will be exactly in the opposite direction from the Sun as seen from the Earth.
Because of the way both planets orbit the Sun (at different distances and speeds), this happens approximately every two years, and this event marks the closest approach between the planets in that period. Depending on when that happens in the year, though, the approach can be very close, not so close or something in between. This year's opposition falls in the "something in between" category. The 2003 approach was a really close one, as it happened when both planets were at their closest approach to the Sun (this always happens when the opposition happens in July or August); the next one, in early 2010, will be a "not so close" one.
Still, Mars is already very bright in the evening sky; maximum brightness, in fact, happens tonight, as the actual closest approach is not at the same time as opposition; since the orbits don't quite match, the closest approach happens today (19 Dec) at 10.45am Melbourne time. Mars can be easily seen at night, even in bright skies, as a clearly reddish "star" rising in the north-east as the Sun sets (which makes sense, if you think about it). Even a small telescope will provide a very good view of the planet, but looking with your naked eyes will be a beautiful sight as well.
This great view will continue over the next few weeks, slowly losing brightness as Earth overtakes Mars and pulls away. So, lots of opportunities to go out and watch our red neighbour; if the weather is not that good tonight, you're still sure to get at least one clear night over the next week or so. And, really, you can't miss it in the sky.