Plugins to Add Multiple Columns on your WordPress Page

Set from within the Page/Post itself using shortcodes (My favourite)

[column width="47%" padding="6%"] Column 1 content goes here. [/column]
[column width="47%" padding="0"] Column 2 content goes here. [/column]

Set from the template file

http://wordpress.org/extend/plugins/multiple-content-blocks/

Using MultiEdit (Similar to previous option)

http://blog.page.ly/multiedit-plugin/

Set from WP-Admin

http://wordpress.org/extend/plugins/secondary-html-content/

Using the More button

Quite a complex solution, but looks great, uses the <!– Nextpage –> tag

More information