One way that I regularly use screencasting is by creating short tutorial videos for teachers on how to use various tech tools. As a technology coach and coordinator for over 70 teachers, it's often difficult to have time to give each teacher the individualized instruction and coaching they need to feel confident with effectively integrating technology in their classrooms. Screencasting has provided a way for me to reach teachers, even when I can't be there in person. I create short screencasts to help teachers with a specific tool or instructional use, and post them in our school LMS for teachers to watch when they have time.
Here is one I created today to help teachers navigate the new features in Google Forms. Whether you are a longtime Forms user, or you just heard of it, this video will give you some background knowledge to begin using forms in your classroom. I'd love to get some feedback on it - feel free to share with teachers at your school as well!
Other instructional uses for screencasting are creating tutorial videos for your students (you could post QR codes around the room for easy access), giving parents a walk-through of important online resources (I promise they won't ignore it like they ignore your emails!), and sharing digital products in an easy-to-view package. We even use it sometimes to record YouTube videos for our students since student access is restricted in our district. I look forward to reading your feedback and other ideas for screencasting in the comments!