Many of us are used to left-to-right (LTR) languages. WordPress is more than capable of handling both LTR and RTL content though. You can find out more information about RTL language support on WordPress. Those of you who are building a website in Arabic should give these plugins a look:
WP Arabic Virtual Keyboard: this plugin is designed to make it easy to type in Arabic without a 3rd-party software.
GSpeech: a text to speech solution that allows users to listen to written content on your website. More than 40 languages are supported.
WordPress Special Characters in Usernames: the name explains it all. This plugin allows Arabic, Russian, and other special characters to be used in usernames.
Transposh WordPress Translation: adds translation support to your blog. Supports RTL and LTR layouts. You can translate all content, including comments.
WP-RTL: adds two buttons to TinyMCE to enable writing text in left to right and right to left formats. It works for English, Arabic, and other languages.
RTL Tester: this plugin tests your themes and plugins in RTL mode. A useful tool for developers and folks who want to find themes that are compatible with their language.
You should also spend a bit of time to get familiar with how WordPress supports RTL languages. The above plugins simply make it easier to use WordPress to manage a site with Arabic content.