I've been working on a GPS track visualization and processing tool - GPSMash - for a while and today I just completed the first release suitable for public use (most bugs fixed, enough functionality, good documentation). This is a command-line Windows application that can repair broken GPX files, clean-up, organize, and analyze data, convert to various formats for visualization, etc.
Here is a sample video using data processed with GPSMash:
Click to play video: http://youtu.be/hAvHgBFEOAc
If you are interested, you can download it from my site:
Any feedback is welcome.