The most advanced and powerful TeX frontend available for OS X, and one of the most ambitious OS X opensource projects. The author, formerly involved in the development of TeXShop, created a program that outshines TS in almost every aspect. iTeXMac's depth and sophistication will please old TeX wizards, and it's auto-complete features and command menus will help newbies to get started with their first TeX project. If you want to travel the beautiful and elitist world of TeX typesetting, iTeXMac is your vehicle.
Of course, there is still some work to do. There are some interface bugs, and the editor feels slow and clunky at times, but iTM is improving with every release. Check the Author's site and dl the latest beta at http://itexmac.sourceforge.net . The betas are all very reliable (even if they are marked as "unstable") and far superior to the version you get from this dl link.