Written like average software requirements. I just now realized this is going to make me look incredibly needy and high maintenance :P
Semi-quiet area, office space or similar. Access to earbuds or other noise-isolating audio device. Unfiltered internet access. Ability to defer interaction for small periods of time in order to preserve mental state (i.e. a lack of constant "DROP EVERYTHING AND FIX" issues). Widescreen display or dual non-widescreen displays for anything more serious than scripting.
Recommended (i.e. dream) requirements:
Darkened room with natural, muted lighting. Small group of people, no more than 4 or 5. Preference of IM, email, other non-state-destructive methods of communication (anything but in-person meetings) wherever possible. No loudspeakers or paging systems in the work area. Windows XP, apt-based Linux distribution, or Mac OS. Dual widescreen displays. Standard keyboard layout or original MS Natural (none of this slight-curve malarky). Adjustable chair with armrests.