Who are you, and what do you do?
Hixie; I edit the HTML standard.
What hardware do you use?
Whatever I happen to be in front of. Right now it's a 27" 2010 i7 iMac with 16GB of RAM, 9GB of which is free, to which is attached a Kinesis Advantage keyboard in Dvorak mode, a Drobo, and various other peripherals. I also have a Chromebook to my right, which I was using earlier. Most of my work is done on a 15" MacBook Pro while couch-surfing around our campus, though.
And what software?
Pine for e-mail, Emacs for editing, irssi for IRC. That's about it. I run them on remote Linux boxen that I access through SSH using whatever terminal client is on the machine in front of me. Using screen I can arbitrarily reconnect to the remote sessions at my whim.
I use Pine rather than other mail clients primarily because of important features that few other mail clients have: it lets me reply to multiple e-mails all at once, combining the e-mails I'm relying to into one and merging the recipient lists (this is especially useful when bulk-replying to feedback on the WHATWG list); it is really efficient to use from the keyboard, it lets me resend mail with Resent-To headers very easily, and it does threading.
Emacs I use mostly because it's what I'm used to, and whenever I need it to do something new, it turns out it can already do it.
Irssi I use because it's the only IRC client I've come across that supports many networks and channels well while being a text mode client that I can use over SSH.
Oh, and Web browsers, of course. Whatever I can run on the hardware in front of me.
I like to treat the local machine as a dumb terminal. It makes it easier to deal with hardware failures and so on. Once I was working on a laptop and a cat sat on the keyboard to get me to pet him, pretty normal behaviour for him. I just took out another laptop I happened to have at the time and reconnected to my screen sessions, picking up exactly where I left off -- and the cat had the most amusing look on his face. You don't often get to beat a cat at their own game!
What would be your dream setup?
Anything with low latency and a decent keyboard, really. Honestly the only thing stopping me from editing the spec on my smaller devices is that on-screen keyboards are just unusable.