Panoramic view of Spirit's landing area.
The main goal of the missions was to analyse the Martian surface, its rocks and soil, to search for evidence of water in Mars' past. Originally the mission was supposed to last for 90 (Martian) days, but now it's been more than 6½ years (2157 days) and there are both still going strong.
Or at least they used to.
In May 2009 Spirit got stuck in a sandtrap (sort of) and was unable to move any further. After many failed attempts to free it, it was decided today to leave it in place and consider Spirit a stationary research platform.
You can see some of Spirit's panoramic images here and a gallery of some of the cool images taken by the rover here.
Dust devil on Mars (click the image to see an animation of the dust devil)
For a 3 month mission, this turned out rather awesome. Thank you, Spirit :)
You can send a postcard to Spirit here.
Self portrait of Spirit
The rover twin Opportunity is still going strong.