Microsoft Natural Ergonomic Keyboard 4000 ($35, Amazon 4 stars, 1,289 reviews)
Split keyboard with enlarged keys, the whole setup built for the proper hand and wrist position. I'm still getting used to it, as it's a big change from a more 'normal' keyboard, but I'm really liking it, and it feels like it's improved my typing speed above my normal 117 WPM, though I haven't tested yet.
How about mechanical keyboards?
I have often benefited from recommendations for Things I Didn't Know I Wanted.
Given that Less Wrong is a community of unusually intelligent, critical, and self-improvement-focused people, I suspect we can generate a pretty helpful thread of product recommendations — perhaps even a monthly thread of product recommendations.
Rules: