As my Twitter followers may know, I think I am undergoing RSI-style problems with my right hand - specifically on the joints in my thumb and on the muscle tissue in the palm of my hand, specifically while using the mouse. 
I'm thus going to take a few days off blogging and computer usage until I can get to a doctor and have it dealt with by a medical professional. From folks I know who have had RSI and RSI-style symptoms, early treatment is the key. I have switched from external mouse and keyboard use back to using a laptop with the built-in trackpad and avoiding use of that where keyboard shortcuts are available. I have found the Gmail shortcuts to be very useful, for instance.
I've also installed Time Out, a free OS X application to break up computer usage with micro breaks and hourly ten minute breaks. I am experimenting with the use of various assistive technologies including a Wacom tablet which I'm borrowing from a family member.
The severe pain resulting from this has reminded me how important it is to remain healthy, and I would encourage anyone who is a programmer, developer or other computer user to think about these issues and don't make stupid mistakes which are easy to avoid with only small amounts of money and time. Learn to touch type properly - I know it's a bit like the drunk telling you to remain sober, but touch typing is a worthwhile skill to learn to touch type in order to prevent RSI (as well as be a more efficient typist). Buy a mouse that's comfortable rather than one that looks nice (even if that means a big, clunky chrome Microsoft thing over a sleek, white Apple Bluetooth one). My del.icio.us tag 'rsi' has lots of useful resources on RSI and I'll add them as I go along.
Just so you know, I may not respond to e-mails too quickly either. I'm sorry about that, but having a working hand is more important to me than reading your e-mail. I will respond eventually, but I'd rather have my hands working.
