This flight planner is just amazing, and a breeze to use, can't believe it's free. Simply wonderful. Many are using it with the iPad, as a moving map display with many extra functions. It can be added to both FS2004 & FSX. Version 2 was linked to Google Earth, number 3 is linked to another database. (Due to copyright issues and money-matter etc.). Filing flight plans used to be boring, but not anymore.
Download: http://www.tasoftware.co.uk/ (version 3)
Review + Quick guide: http://mutleyshangar.com/reviews/jack/plang/plang.htm (version 2)
Video, used with default FSX Cessna 172 Skyhawk: http://www.youtube.com/watch?feature.&v=O0XLAGNIYzI