I very rarely do this, but once very very early in my career I actually brought my entire studio to the other side of the country, lock stock and barrel (except the mixing console. Even I have my limits...), and built an ADR-studio in an apartment. That simply will not happen again though.

Nowadays, I see it like this (at least for now); if I really must do dialogue editing in another studio for some reason, I'm just bringing a drive with roomtones and location-based hard effects and foley (you never know), my Nuendo install-disc (all software including ditto Syncrosoft and iLok-keys, of course), my Dolby meter, a few simple dynamic processors and filters (just in case), and two of my main monitors. And a trusty trackball. I hate working with mice or trackpads.

Last time I did sound effects in another studio I brought my complete computer with the then only picture-monitor and patched the DSP Factory-card (impressing at the time. Been very dated for years now) bypassing his console and directly into the patchbay. Now I'd just bring my fieldrecorders, or possibly rent a Cantar, depending on what I'd do.

When doing sound design, on the other hand, things gets a lot more complicated. I try to avoid doing it externally, after all I do have well good stuff myself which I know well (I traded my old Yamaha-cards for state of the art second generation Lynx-cards years ago), but sometimes that's not an option. Things depends on what the studio and the occasion. If I'm just supervising, I just bring my reference headphones and a single large harddrive with all my sound effects. I very rarely do that either though, I like to work hands-on also when supervising. When doing some serious sound designing myself, my luggage would consist of my entire computer setup including all three picture-monitors and Lynx-rig, all five main monitors (right now Yamaha HS80 with phase-corrected bass management, but I'll buy some iNo as soon as I can afford it. The Yamaha's are VERY frustrating to rig...), a switchbox for the listening monitoring (never underestimate the value of some extra reference listening, hopefully already tuned for the room), my headphones, a DVD with all install-files for all my software including Windows (just in case, Murphy's not a lazy man indeed), my location set (K-Tek boom, Fostex FR2 fieldrecorder, different Sennheiser MKH mics, will supplement with linear DPA's, and Beyer 250 headphones, lots of batteries), and a backup harddrive with all sound effects should the internal dedicated effects-drive up and die on me. And of course some reference listening-material on DVD coded in DTS. When I've installed a BluRay in the computer I'll probably change that to reference listening in BD, coded only in lossless. Sounds likely.

But most important of all, I'll make sure I'll have access in one way or another to peanuts/roasted pumpkin seeds, grapefruits/pomelos, and coffee. Some healthy doses of Doctor Pepper is also good for the morale no less, but the caffeine, citrus fruits, and the mineral- and energy-rich peanuts/pumpkin seeds all helps regaining what the brain burns at a ridiculous speed while concentrating heavily for extended periods of time, especially after entering hyper focus and beyond. At my places I have no more than a five minute walk to get that, when in other studios it's a good idea to find out if one can get it anywhere near, of if I'll have to bring it myself.

Great question, this is something that I've been pondering for a little while now. I've been doing a fair bit of stage editing in the last few months and have been considering a 1510LFC pelican case not just for safe carry, but just as a "home" for all my mobile gear as well. I'm pretty sure it'll all fit.

What I currently tow along (in two backpacks) is my 15" MacBook Pro, a clone of my SFX drive, a full size keyboard + Apple Magic Track Pad, an Apogee MiniDAC, headphones, two USB hubs (one bus powered and a self powered backup), two iLoks and a USB thumb drive with my Waves 9 licenses, a travel power strip and then all the associated power, USB, FW800, cables etc. Oh, and a granola bar or two. But this is when I'm expected to be working on my own gear.

What I've seen work well when a machine is provided for you is a bootable FW clone of your internal HD. Attach it to the machine in question, reboot, and you might as well be sitting at home. Some bring an additional drive / partition with all their plugin install .dmg files, just in case something needs to be added. Still need the iLoks though. Can't say I've seen too many response authorizations, which companies have gone that route?

EDIT:

All this talk of extra screens reminded me that I also bring my iPad along. With TouchOSC, V-Control Pro and DisplayPad it's quite a useful thing to have along with the MBP.

When I do theatrical design, I bring my mac, external sfx hard drive, mouse and matt, beyer 770s, and my minirator pro. That's the killer, because I can set up the PA to optimum standard before I playback my sound. Nothing worse then altering your audio, to find the rig has been garbling it up anyway.

And I shove it all in a pelicase.

Beyond the basics that everyone else seems to carry:

• My own headphones
• My own mouse/input device and any drivers needed
• Backup of any drives
• 2 spare 32GB thumb drives
• Small rolls of as many kinds of tape as I can remember to bring: Duct, gorilla, micropore, gaffer, spike...
• Pens galore
• Things to stave off hunger or boredom (food and eBooks)

I usually try to fit everything into two softsides and two Pelican 1500's, at the most, depending on what I'm doing (field recording is one softsided shoulderbag and my SD recorder in a PortaBrace). My rule is that everything, including boompoles and tripods, need to be <18" collapsed, so that I can have flexibility in what bag(s) I bring. Makes things a lot more modular.