Who are you, and what do you do?
What hardware do you use?
I've got two setups - my office machine is a Mac Pro w/ Quad-Core 2.26 Xeon machine, with some big disks in it for Time Machine and my home directory. I also use an Intel SSD for the the boot volume and also to build my projects to (it's fast!). I've got a 23" Cinema HD display as my main monitor and an old school 22" Apple Cinema Display with an ADC connector as my secondary display. I can't believe it's 8 years old and still kicking. I also use a Logitech MX518 mouse, and an MS natural ergonomic keyboard - I can't live without a split keyboard and Microsoft has always made my favorites. I also have a Line 6 TonePort for recording my guitar, and a Wacom Intuos to use in Acorn. I made the desk it all sits on, since I'm a picky guy about some things.
My home machine is pretty similar - except it's a bit older and I have a 27" Cinema display as my main monitor and a Wacom Cintiq as the secondary. Same keyboard, same mouse, and a slightly newer Line 6 TonePort for recording. I also made my home desk, but recently I ripped off the legs and put the top on a GeekDesk frame which makes it an adjustable standing desk. It's pretty nice and I talk about it to my tech friends whenever I get a chance.
And what software?
Acorn, VoodooPad, Xcode, and Safari are pretty much what I live in all day. Apple Mail, Colloquy, iChat, Twitter, and JSTalk Editor are more likely to be open than not. When I need to touch up the website for something I'll launch Coda, and I also find myself in Transmit quite a bit. BBEdit is my text editor of choice and has been for 10+ years, but I'll use SubEthaEdit now and again for various editing needs.
Things that are running in the background, which I never seem to think about are LaunchBar, DropBox, Time Machine, and Backblaze. I also use rsync every day to backup projects to a 3rd location. It pays to be paranoid about data, especially since my company is essentially built out of a bunch of text files and images.
What would be your dream setup?
I really want the fastest machine possible, with lots of options for disk space. So if I could have a 13" MacBook Air which had the processing power of the fastest desktop machine, super big and super fast SSD's, and Thunderbolt ports which connected to my backup volumes and big displays (27" HighDPI monitors please!), I think I'd be in heaven. And while I'm at it - city wide gigabit wifi please. Then I could just take that machine to work or on the road, and not worry about having multiple machines. Some day, it'll happen.