I have used Privet to test my bonsai knowledge over the years, and although not the best tree/bush for presentation, it has many attributes that make it a good species for learners;  it grows like nuts (it's classified as a weed), roots like mad and puts out alot of growth for you to play with.  Hardy, and springs bad furiously in springtime, usually holding a significant number of leaves through the winter.  Best of all if you live in more humid areas, or namely the southeast US - it's likely in your back yard or along your fence line...  :)

I'm working on alot of other species too, but my larger and more interesting privet are all up for pot moves right now, so they get some air time..  :)