Ahh, crunchies, reminds me of the good old days of running Cross Country and Track during High School... The way I learned it was to lay on your back, bend your knees and lift your legs above your chest. Sounds sexual, but it really works! Put your hands behind your head and do the motion for regular sit-ups. Do about 10-15 of these.
Then do movements of touching your left elbow to your right knee, twisiting your torso, for 10 reps. Then the other way. Then do alternating movements these with 10 reps of each side.
Then do bicycle kicks while streching your legs all the way out and also touching the knees and elbows at the same time.
There's about 5 more stages that we would do, but they're pretty hazy right now... I guess that's what we got for stopping in the woods all the time for a little mind-altering recreational break...
Oh, these crunchies would be done AFTER we had done a mile warm-up and at least a 5 mile run. These are killer stretches to do especially when you're so darn tired, but they really work!