Mike,
Welcome and thanks for posting. Our young onset PD support group visited a rehabilitation facility that offers assistive technology (that's what it's called) to folks. That includes a variety of types of keyboards. Some had larger keys, some were one-handed - either left or right, you name it and it was available. However, the basic issue of stiffness or slowness in typing still exists.
I agree with Ed/Yekkimo that one of the most beneficial forms of computer technology for folks with PD is voice recognition software. There are two leaders: Dragon Naturally Speaking and IBM Via Voice.
Anyhow, it's software where you talk, it types. Or it will read text, from primarily Microsoft products like Word, to you. Or email - probably from Outlook or perhaps Outlook Express. There is a 'training' period where you read certain text so it 'learns' to interpret your accent, inflection, tone, etc. The newer versions are much easier to 'train' in less time. You'll want to research this further. Websites are (and I can't get this to create a hyperlink that you simply click on ... so you'll have to copy and paste):
http://www.nuance.com/naturallyspeaking/ <---- Dragon Naturally Speaking
http://www-306.ibm.com/software/voice/viavoice/ <---- IBM Via Voice
Hope this helps,
lizzy4451