Another free program from Microsoft that will be a big help in your face-to-face classes is called ZoomIt. This program lets you zoom in on your computer screen and annotate it. Be sure to read the fine print on this page for instructions on how to use the tool. It will be easier to read once you have ZoomIt installed!
If you install this in a classroom, leave the default keyboard shortcuts as they are unless they interfere with something you teach. This way other teachers who know how to use the program can use it without having to learn new keys.
Here's a little Cheat Sheet for using it.