Advanced WP Columns is a free plugin that allows you to split your post content into any number of columns with any dimensions you’d like. This is accomplished by simply dragging-and-dropping.
I’ve used column shortcodes in the past and they are easy to use, but they’re not flexible. With Advanced WP Columns you can set the exact number of columns you want and at whatever size you want, no problem. There are also built-in options so you can simply select two-columns or three-columns instead of sizing and creating them yourself.
Even if you are savvy with CSS, you’ll spend a lot less time and energy simply using WP Columns.
Advanced WP Columns is also responsive, so visitors on all devices will have a good experience. The column widths are percentage-based, but you can also set a break point in the settings menu.
The break point simply decides when all of the columns become single width. The default is 1024px, but if you have a responsive site you may be able to lower it a lot and preserve the column layout longer.
In the settings menu are a few other options including the ability to add your own CSS classes to make styling different elements of the columns easy.
On WordPress.org: http://wordpress.org/plugins/advanced-wp-columns/