Curiosity (more formally known as the Mars Science Laboratory) has landed successfully on Mars! A very complex landing system (The so-called Seven Minutes of Terror) was required to get such a massive (one ton!) rover safely on the ground, but it seems to have worked flawlessly – it landed with a vertical velocity of 0.75 metres per second, and a horizontal velocity of only 4 centimetres per second, and well within its estimated landing ellipse – well done to everyone involved!
There’s a news conference at 9am PDT today, apparently they’ll be showing images from Mars Reconnaissance Orbiter’s HiRISE camera of Curiosity on its way in to landing on Mars! There’ll be another at 4pm PDT possibly with MARDI (Mars Descenmt Imager) images too – You’ll be able to watch a livestream of the news conference (and future ones) here: http://www.nasa.gov/externalflash/mars/curiosity_news3.html.
Meanwhile, here’s a very nice summary of what we have so far from Emily Lakdawalla at the Planetary Society.
And if you want to see the scenes at mission control during the “Seven Minutes of Terror” as Curiosity landed, you can watch them here – it’s pretty tense!
This is going to be an awesome mission. Curiosity has enough power for 2 years of roving, but it’s undoubtedly going to last longer than that (the only real limitation is the life of the mechanisms and motors, but they’ve apparently been tested to at least three times the mission duration). Stay tuned for some amazing images over the coming weeks, months and years!
EDIT: And here’s the MRO picture! The orbiter was almost directly overhead, about 340 km away – even from this distance you can see a lot of detail on the parachute and the backplate (you can read more about it from Emily here). 
They’ll be spending Sol 1 (a Sol is a day on Mars) checking out the equipment and should be getting the High Gain Antenna up and running later this afternoon – that’ll allow the rover to communicate directly with Earth. Over the next few Sols they’ll be raising the Mastcams, taking some higher resolution pictures, and getting the onboard equipment up and running, and then hopefully in a couple of weeks once they’ve made sure everything is working properly they’ll take Curiosity on her first drive. There’s no rush though 🙂