There are a few online video editors available right now, and there are also several slide show tools online. Vcasmo is both. It's designed to display video alongside a PowerPoint slide show. It fills a highly specific need, and it does it well.
If you want to put a speech on the Web so people can see it, and you have a video of it and a PowerPoint or a PDF (or a collection of JPEGs), with Vcasmo you can put the media together side-by-side. A simple timeline editor lets you define exactly when images display in your presentation. Once the presentation is all synched to your satisfaction, you can embed it on your own pages.
The editor is a bit limited, though. You cannot cut pieces out of your video, and you can't edit text within PowerPoint slides. And maybe I'm asking for too much, but I'd also like the option to record audio or video directly from Vcasmo to narrate an existing slide show.
This a project from Japan, and the English version of the Web site in need of an editorial pass. But that's small potatoes. This is a very useful tool for documenting speeches and lectures.