G.ho.st is by far the best Web OS I've ever used.
G.ho.st is basically a full operating system that runs in a web browser. G.ho.st does use flash which I am not really a supporter of when it comes to web apps and web OS's just because of the fact that it takes longer to load, and renders web apps useless to those who do not have the flash plug-in installed.
What really gets me about G.ho.st is that they work hard to make it so you can use services you are familiar with, with ease, all through their sleek OS. Third party apps are a big part of G.ho.st, G.ho.st has provided API to developers so that developers can actually design apps that interact with a users files and get information from the users account such as font preferences, language, username, and more, but all is stuff you wouldn't worry about sending to those third parties anyways, because the only thing that identifies you is the username, that's it! Many services don't even grab your username. G.ho.st also has a special Trust menu so you can designate apps you trust with what information. Kind of like a firewall it protects you so you don't share information that you don't intend to.
Currently only web apps that already have web hosts are accepted, what I mean is you can't upload a web app to g.ho.st and have them host it for you. That is a disadvantage to G.ho.st but that disadvantage is made up for easily with all the features g.ho.st does have.
G.ho.st has a windows like file system, including different drives on your VC(Virtual Computer). One drive is your G.ho.st Drive, this is a special drive that you get with your VC that basically has an infinite supply of space for you.
Basically you can upload files to your g.ho.st drive, share the files, view the files and even edit them; All within G.ho.st. Another drive that comes with G.ho.st is your Google Docs Drive, basically this allows you to link your Google account(s) to your G.ho.st account where you can transfer your files to and from your G.ho.st drive, and edit the files using your favorite editor. G.ho.st sets up your google docs drive as if it were just another drive on your computer, it's quite cool.
G.ho.st has so many features it's really hard for me to go into all of them but I want to talk about G.ho.st Lite. G.ho.st Lite is a special version of g.ho.st designed for mobile phones, which is also accessible by computers(in-case you are using a computer that doesn't have flash). I really like this because recently I got a very nice mobile phone called the Samsung Rogue, the rogue has an amazing web browser which I love however it's flash support is obviously limited. I need to be able to access my files on the go and G.ho.st Lite allows me to do just that. G.ho.st lite is a very simplified version of g.ho.st that has all the absolutely necessary features of G.ho.st just simplified, there's access to email, your calendar, your webmarks(G.ho.st's version of bookmarks) a translator, sticky notes, all your files are accessible and downloadable, and much much more!
G.ho.st has so many features I can't even try to sum them all up in one blog post so I'm afraid this is as in depth as I'll go for today.
G.ho.st offers all these awesome features and way more, for the awesome price of FREE!
I recommend trying g.ho.st out