After the 8/13/09 Classless Update, a new Force-a-Nature jumping technique emerged. It was first discovered by Steam forum user d3ward. The thread can be found here- http://forums.steampowered.com/forums...
In the video I use a script created by user sp12. It makes Force Jumping about 1000x easier, so I highly recommend you use it if you're going to be force jumping a lot. The script can be found in the above thread.
As of right now, this isn't patched and can be done. Most likely, this was an unintentional bug so don't expect this to be forever (however I personally think this one of the greatest changes/bugs ever made to a weapon because it adds a new level of maneuverability to the Scout.)
This video shows a small fraction of the jumps you can pull off on the maps 2fort, Gravelpit, Badwater, and Well. My favorite jump so far is on 2fort where you can successfully make it from ground level, up through the grate, and into the second level. Since this technique is still fairly new, nobody expects a Scout to appear from there (giving you a great advantage.)