You can use SlideShare to upload your slides and share them publicly or privately. Private sharing, where you give you students a secret URL, may be useful when using copyright images that you shouldn't be broadcasting widely or when sharing presentations that you don't necessarily want the whole world viewing. Such private sharing is not a particularly strong wall against misuse of your material . . . but is pretty effective most of the time.
Presentations that you've uploaded to SlideShare can later be narrated, which is a great feature. That means that you could use SlideShare to host virtual lectures or introductory previews. You can even embed them in your online syllabus or course management system.
Your students and colleagues can either view your presentation on the SlideShare website in a viewer (or full screen), or they can download the file and play it in PowerPoint directly. Colleagues could perhaps edit and add to your presentation, then upload their version for sharing.
One of the best features of SlideShare is that it's FREE!
Here's a sample of a narrated presentation from SlideShare that you might want to share with your colleagues.