Ergonomic keyboards are nice, but even more importantly, I'd recommend one with mechanical switches. Best thing I ever bought. Cherry has good cheap ones, but mechanical switches last forever, so you could also go with an old Model M. I also use my own custom keyboard layout, but Dvorak is just as good for most users, really, but I'm an Emacs user, so there. (I use 7 modifiers. Don't judge me.)

Honestly, I don't get office chairs. I think they're all horrible. I use big, comfortable reclining chairs with plenty of pillows. Recent research backs me up on this.

(The links are all first Google hits, so I apologize, but I didn't have the time to look for good sources.)