My pick for online video editing is Binumi (www.binumi.com). This is an excellent video editing website for both teachers and students. Two things set it apart from other editing sites. Firstly, it has a library of more than three million videos, images, and audio files. Secondly, students are able to upload their own videos in addition to Binumi's library of child-safe and copyright-friendly files. Students are able to make completed videos private or public and can share with Binumi or via social media, including Youtube. The site is mostly free but some options are only available for a paid subscription. This site will work best for 4th through 12th grade.
For postcasing, I choose GarageBand. Not only can you record voiceovers but you can also create interesting podcasts through the use of additional musical elements. It's easy to use and students love it. This is recommended for grades 3 through 12.
Finally, for student blogging, I pick Edublogs. This is a great tool because you can set up individual student accounts in a single blog. This creates a community of bloggers. You can also set up individual blogs for students, thus creating a student network. This is also a great tool to use with parent communication of what is happening in the classroom. The only drawback is that some pro features are only available through a paid subscription.