If you have a Flickr account you can post images directly to your blog, in a few simple steps. 

Step 1 - Login to Flickr

Navigate to the blog settings for your Flickr account, or access the page directly from this URL: http://www.flickr.com/blogs.gne

Step 2 - Blog Type

Select the "MetaWeblogAPI Enabled Blog" from the drop-down list.

Step 3 - Configure

For the API Endpoint, use this URL:

http://www.squarespace.com/process/service/PostInterceptor

Your username and password will be the same as to log in to your Squarespace site.

Step 4 (Optional) - Choose a Layout

Flickr allows you to configure the template for posting images to your site.

Step 5 - Post 

After your blog has been added to your Flickr account, you can post images directly to your journal.  When viewing an individual image in Flickr, click the 'blog this' link.