Some time ago, I explained how to insert multiple articles quickly using an extension called Mass Content. Unfortunately the developer seems to have disappeared and the extension is no longer available. However, someone has been kind enough to include a copy in the Joomla forums so grab it while you can. You will need to register with the forum and login, in order to download it.
Joomla security experts recommend that you only use extensions that are continually developed, so if a security flaw is discovered, it can be quickly rectified. So you might like to consider an alternative called Quickcontent.
If you only create the occasional article, then this is overkill. But if you need to enter a bunch of articles then you might be surprised how much time you can save using Quickcontent. The interface takes some getting used to, but once you've used it a couple of times, you'll find it very handy. The main feature that threw me was working out how to actually save an article (look for the green circle with a check mark). Also, click the Preferences button in the top right as you may wish to change the first option to Yes.
Developers will love the built-in lorem ipsum generator which helps you to create a site with dummy content very quickly.
