Are there any web-apps that are useful offline?

There are many useful web-apps, and some of them have implemented support for offline use. I understand that this is very useful if you lose your connection, and want to keep using the application until it comes back, but most web-apps are designed to be used when connected to the internet, and revolve around network-based features.

Are there any web-apps that are useful offline? (I.E. That you can use without being connected to the internet.)

From web app Jonas

• Gmail, Google Calendar, Google Docs support offline too. For that I think you may need to enable Labs features.

  fretje : Why the downvotes? GMail has off-line support out of the box (no need to enable a lab feature, you have to enable the offline support through the settings though), and is very useful that way!

  drye : I use Google offline for gmail, reader and docs all the time. I voted up, but don't understand the votes down.

  Antoops : i was confused with down vote without comment........ thanks fretje and drye for support!! :)

  Stefan Lasiewski : Google Docs has [phased out offline support](http://docs.google.com/support/bin/answer.py?hl=en&answer=176376), and will implement it again sometime in the future (probably with HTML5). It still works offline, sort of, but it nags you every time it tries to save, and you risk losing your changes.
  From Antoops

• If I understand correctly you want an app that runs in the browser, but not online.

  The trouble is where the code is stored. The code running most web apps sits on a server somewhere in the Internet.

  You need to be connected in the beginning, just to get the code downloaded to your computer.

  In theory, with localstorage a simple app could pull down enough JavaScript logic in a single page to provide a useful app (e.g. a whiteboarding application) where there isn't a dependency on searching/retrieving data from a server.

  However most online apps thrive due to being online, and inter-connected with other users and other sites.

  Is there a particular type of site you wish worked offline?

  From scunliffe

• If you are including webapps with native desktop counterparts in this question, then I would argue that Evernote (a powerful note-taking tool) is a webapp that is very useful offline, along with others, such as Dropbox (a file syncing tool that will sync any changes made while offline when you go online).

  If we are excluding these types of apps where the desktop counterpart is the offline component and they are not offline in the browser, then I would nominate Every Time Zone (a great webapp for visualising different timezones), which works offline perfectly in Google Chrome for me, using offline storage (your browser will probably ask you whether you want to allow the site to store data online, so answer yes to this).

  Edit: I came across another app called ThreeTags Online Noteboook, which provides an offline mode using Google Gears, so that might be worth checking out.

  From tobeannounced

• Picasa and Google Earth (the online version is a view in Google Maps) are two more with on-line and off-line counterparts in the sense that tobeannounced mentioned.

  ChrisF : I think with Google Earth you have to be connected to get the imagery. There's simply too much of it to be stored locally.

  citadelgrad : You can increase the cache of Google Earth to improve the amount of data offline.
  From Dennis Williamson