Out of the basements in New York comes Empressr, the latest addition to the online-Flash-based presentation gags (ZohoShow, Thumbstacks). Empressr is a Flash-based tool you can use to build online presentations, that's 'Flash-Based PowerPoint for the Web' in buzzword-terms.
Currently in Alpha 0.01 (in other words, don't bash us), it comes with a pretty self-explanatory interface if you're familiar with PowerPoint or Keynote. It includes templates — although not those slick theme types which you may have been used to but simply pages with different types of elements (charts, bullet-points, Flash) — which you can insert into your projects.
What's missing from Empressr as Michael Arrington points out, first and most importantly, are some import and export features — PDF, PowerPoint, HTML, Flash — we want the lot. Let's face it you aren't going to get anywhere with following some pretty well-defined standards. Functionality and feature-wise while I do think Empressr impresses to an extent, I would like to see some deeper features like what Scrapblog is perhaps doing with their scrap-based presentations and Flash (some neat drag-and-drop features, slick GUI, templates, etc.)
In conclusion, for basic-level functionality and more importantly use, Empressr does the job. Obviously you can't expect a whole 300MB PowerPoint package from a hundred KB Flash app, but if you're looking for something quick, dirty, no-hassle and no-waiting-10-seconds-for-the-textbox-to-load to make something to send to your grandmother and relatives, Empressr may be for you. However, for the hard-core 100 slide keynotes or pitches or even something professional, Empressr — or any kind of an online presentation app — is no where close to being able to achieve that level of presentations and use.