useful examples that work out of the box (see comments in my installation instructions):

calibration_artificial (camera calibration)
stereo_calib (camera calibration)

demhist (histogram calculation)
dft (disrete fourier transform)
distrans (edge distance transform)

edge (canny edge detection)
contours (find contours)
connected_components (binary connected components)
convexhull (find minimal convex hull)
fitellipse (fit ellipses)
houghlines (fit lines)
squares (fit squares)
minarea (minimal containing square and circle)
inpaint

fback (farneback optical flow)
find_obj (SURF)
find_obj (fern)
chamfer (matching edge template)

lkdemo (tracking)
camshiftdemo (tracking)
motempl (motion detection)
facedetect (detect faces)
segment_objects (background subtracted segmented detection)

em (expectation minimization clustering)
kmeans (kmeans clustering)mushroom (machine learning example)
points_classifier (machine learning example)