Sabily is free, already includes all software you need in your everyday tasks, and is customized specifically for Muslims. The main softwares are: Zekr and Mus-haf Othman (Quran study tools), Minbar and Firefox-praytimes (prayer times applications), Monajat (application that popups prayers every predetermined time), Hijra (islamic calendar) and WebStrict (parental control tool). Arabic language is also well supported. The latest version comes with Unity Desktop, Firefox4, Libreoffice, Banshee(replacing RhythmBox) etc..
Sabily (formerly Ubuntu Muslim Edition) is a free, open source operating system based on Ubuntu. Its main feature is the inclusion of Islamic software, such as prayer times, a Qur'an study tool and a web content filtering utility.