My life as a degenerate
allaboutparkinsons.com - This is the first forum I found, with mainly US-based members. Rather quiet, but I learned a lot about new research techniques and alternate therapies. Very friendly and caring.
Parkinson's UK - I was introduced to this forum from the other forum. It is quite active without being overwhelming. Aside from the normal forums such as new members, recently diagnosed, daily life, treatment, etc, there is a vibrant social club and a thriving creative corner, so members can play games, write poetry or just chat. Members are friendly, knowledgeable and very creative, but be prepared for a Brit's take on things.
PD Junction - A PD community, complete with forums, blogs, chat, photos and more. You will make friends easily with these welcoming people. Based in the UK and administered by Jacqui.
Young Onset Forum - a National Parkinson Foundation forum which I enjoy reading. It has interesting threads with well-written, quality responses.
Parkinson's Chat Room - Online group chat allows the opportunity to socialize with other PwP world-wide, chatting about PD and non-PD stuff. Uses music and humor to relieve the stress of dealing with PD. DBS friendly. Chat times are 9am, 2pm and 7pm central time (subtract 2 hours for Oregon time).