There is a protocol that many blogging sites now use called MetaWeblog. It allows for people to create content for their web-site from software installed on their computer. This has some significant advantages over using the online editor on your site. The biggest of which is that the program will resize your images for you and upload them to the server. This saves you a huge amount of time and also keeps your web-site looking and working great!
If you are a windows user, the best offline editor to use is Live Writer from Microsoft. You can also use Word 2007, it also does a great job. Live Writer is just a bit better so this tutorial will focus on Live Writer. I will cover Word at a later date.
First step is to get Live Writer if you don't already have it. It is fee to download without any registration from get.live.com. Click on the big orange button. and you will be taken to a page full of all things Microsoft Live that you can get for free. I suggest you only choose Live Writer, the rest you already have or don't need. The Photo Gallery is quite good also if you have a use for it.

Once you have made your selection, press the orange button and proceed to download and install the software. It will not take long, open Live Writer once it is installed.
You will now need to create an account so that Live Writer can interface with your web-site. This is a similar task to creating an email account in Outlook or Thunderbird. From the Tools Button, choose Accounts:
From the Option Window, choose the Add button on the right side.

Choose Weblog Type window opens, you select Another Weblog Service.
Input your homepage address and the credentials of the content author or administrator of your site. This is the same username and password you will use when logging in to your web site.
Select Provider. From this list choose Metaweblog API. For the remote posting URL, you need to put in the web address of your site followed by "metapost.ashx?key=xxx" where xxx is the name of the module you will be posting to. In this case I am using the Dotnetnuke Blog module. The other module I use frequently is News Articles. This is the most confusing part of the process and if you need help, call me or refer to the documentation that is linked at the end of this tutorial.
Now you will be asked if you want to download the styles from the web site and you should say yes to this option can continue to the end of the process.
Now that your account is created, you are ready to author and publish content. Write your words, add the content, insert pictures, maps, videos, links, tables and so much more. Be sure to search for Live Writer plug-ins that assist in making some great content.
The software that makes this happen is a module I purchased called Meta Post. It is available to most of my customers already please contact me and I will make sure this is ready to go. Meta Post is a really great program and you can do a lot with it. Please read thoroughly the documentation to learn what it can do, you will not regret the time you spend. The documentation can be found here.