they start with simpler tasks and move on to more advanced stuff.
http://dasl.mem.drexel.edu/~noahKuntz/openCVTut1.html
http://dasl.mem.drexel.edu/~noahKuntz/openCVTut2.html
http://dasl.mem.drexel.edu/~noahKuntz/openCVTut3.html
http://dasl.mem.drexel.edu/~noahKuntz/openCVTut4.html
http://dasl.mem.drexel.edu/~noahKuntz/openCVTut5.html
http://dasl.mem.drexel.edu/~noahKuntz/openCVTut6.html
http://dasl.mem.drexel.edu/~noahKuntz/openCVTut7.html
http://dasl.mem.drexel.edu/~noahKuntz/openCVTut8.html
http://dasl.mem.drexel.edu/~noahKuntz/openCVTut9.html
http://dasl.mem.drexel.edu/~noahKuntz/openCVTut10.html