Both of NASA's new toys will give you a closer look at the surface of Mars, but from two very different vantage points. Mars Trek takes the Google Earth approach, laying over 50 years of NASA exploration data over an interactive 3D globe. It's incredibly deep, including 3D and 2D views, video-game inspired controls and bookmarks showing off points of interest from previous NASA missions -- in fact, it's detailed enough that NASA is already using the program to scope out potential landing sites for its 2020 Mars rover.
If you're in the mood for something a little more personal, you can take the controls of NASA's latest Mars rover with Experience Curiosity. This is no mere map -- this is a Curiosity simulator with manual drive controls, multiple camera view angles and a guided tour of both the rover itself and narrated lessons about the area of Mars it explored. Both tools are designed to work in any web browser and are completely free to use and play with. Check them out at the source links below.