I'm also a HUGE fan of Desmos.  I've used Geogebra, and it can do a lot that Desmos can't do, but Desmos is powerful and very quick and easy to use.  

Here's a link to a series of short tutorial videos 

If your students have Google accounts they can log in to Desmos and save (and share) graphs in Drive.

A good activity for generalizing transformations is to make your first equation:

       f(x) = x²

and your next equation parts of or all of

        y=a f(b(x-h))+k

using numbers or sliders for the parameters.  A big advantage of Desmos over Geogebra is that it automatically creates the sliders for you (though when you use sliders in Geogebra you can see the numbers change in the equation, which you can't in Desmos).  Then you can change "x²"  in the first equation to any function and see that the parameters a,b,h,k have the same effect on any function.

I don't start with this of course, but it's a good way to tie it all together.