Here I'm going to list some distro which looks like Mac OS.
Dreamlinux is a Brazilian Linux distribution based on Debian. It can boot as a live CD, from USB flash drive, or can be installed on a computer's internal hard drive.
The distribution's GUI has a strong similarity to that of Apple's Mac OS X, with a centered toolbar animated.
2) eAR OS:
eAR OS is an Ubuntu-based Linux distribution featuring the advanced, yet simple-to-operate eAR Media Center. Tune in to TV programs, rip CDs to hard disk in lossless FLAC quality, watch digital TV and DVDs, listen to Internet radio, view photos, or listen to music - all from within an intuitive user interface. The distribution is available in two flavors - either as a freely downloadable "Free" edition, or as a commercial "Enterprise" edition with extra features and performance enhancements.
3) Fox Linux: (The development of this distribution is inactive)
FoX Linux is a single-CD desktop-oriented Linux distribution based on Fedora Core, with KDE as its preferred desktop, main components recompiled for the i686 architecture and out-of-the-box support for popular multimedia formats.
gOS is an easy-to-use, Ubuntu-based distribution designed for less technical computer users. Its main features are the use of Enlightenment as the default desktop and tight integration of various Google products and services into the product.
5) Linux Tiger:Linux Tiger is an Italian origin distro. Designed to be similar to Mac OS X. It uses the new SFS Technology for software sharing.
6) wattOS:wattOS is the lightweight Ubuntu-based operating system. It is currently in alpha stage.