I imagine, if we *were* to do something other than a quick layover on Mars, it would be something like the Soviet plan for planetary observation - see, contrary to the "space race" mythos they weren't really interested in going to the moon. There's nothing of value on the moon, it's just neato. What they wanted to do was build a massive rocket (still to date the most powerful rocket ever built - I mean look at this shit it's star wars calibur shit http://www.aerospaceweb.org/question/spacecraft/russia/n1-1.jpg - yes that's 30 rocket engines in the first stage). You would then use *several* of these massive rockets to lift various pieces of a space station into orbit, using rendezvous missions to construct the platform piece by piece. Then you would send up additional rockets and attach them for propulsion to another planet (initially the plan was for Venus, but once it was discovered that Venus is a literal hell-scape with acid rain, Mars was picked as the alternative target). Then you would just float the platform to Mars, and it would be a base of operations for an extensive study of the planet and its moons, and any manned missions to the planet itself would be supported by the space platform orbiting Mars itself.
The benefit of this, is that you don't have to worry about colonizing Mars, you don't have to worry about it being a one-way trip, and you can carry myriad supplies and scientific implements in the on-board storage of the facility (it doesn't matter how oddly shaped you are in space so long as your propulsion system can get you going in the right direction without making you spin in circles). Then you just dump any new supplies and astronauts on the platform orbiting Mars, and periodically, you bring samples and people back home. You can also just ship new pieces for the space station as needed if any upgrades are required.
Unfortunately the whole program was scrapped because the N1 rocket kept tearing itself apart :(