Glide
glidesociety.com/ (xhtml-mp)
Glide OS is Transmedia's suite of online productivity, social and entertainment applications. It's billed as "The First complete Online Operating System". I'm a little uncomfortable with web services being called operating systems. Regardless of what you call it, Glide is a very full featured product. It includes word processing, spreadsheets, presentations, a webpage builder, bookmark manager, RSS reader, photo editor, address book with integrated IM and webmail, and a calendar plus a personal blog and online photo, video and music sharing.
On the PC, the Glide editors are Flash based and quite slick. Glide has mobile versions of almost all the modules implemented as html forms for compatabilty with even basic mobile browsers. Glide OS is ad free and comes in free and paid versions. The only difference is the amount of storage you get. The free edition includes 2 MB which can be increased to 12 MB for $9.95/month or $99.95/year. Glide puts a lot of emphasis on security with fine grained levels of permisions which can be varied on a document by document basis.