I second
Hieronymous' recommendation. I ran Ubuntu for many years and switched to Mint about two years ago, on Mac architecture - no less, and have been very happy with it thusfar.
It really all depends on your hardware and needs. What type of 'work' do you wish to do on your machine? If you're interested in netsec and pen testing then you might read up on Backtrack; general desktop work and internet-based applications - Ubuntu or Mint; lightweight OS for older hardware - Kubuntu; pretty and lightweight - elementary OS, etc. These are just examples to get you thinking.
"Becoming a person of the plants is not a learning process, it is a remembering process. Somewhere in our ancestral line, there was someone that lived deeply connected to the Earth, the Elements, the Sun, Moon and Stars. That ancestor lives inside our DNA, dormant, unexpressed, waiting to be remembered and brought back to life to show us the true nature of our indigenous soul" - Sajah Popham.