The GMC is the main governing body for doctors practicing in the U.K. It's main purposes are to regulate the registry of certified medical doctors and to set standards for medical schools. It's a great website with a lot of useful information, and I would highly recommend the following documents:
One of the top indemnity providers for doctors, this website has excellent resources to help you learn about medico-legal aspects to your practice.
The leading trade union and helps to support the personal and professional development of doctors. Check out their website for hot topics in the junior doctor spotlight.
The Royal Colleges bring together the finest minds of their fields to set standards in clinical practice and education. Pick your college of interest and look out for webinars, conferences, competitions and much more!