Does the hammer editor run on Linux?

There are certain ways you could run the hammer editor on linux. Right now Valve hasn't released it for their native steam client yet but you could try to emulate it with wine or run it in a virtual windows with a programm like virtualbox. There may be graphical issues and other bugs. Ask me if you have any question on how to do it.

The rendering engine Hammer uses is very stripped down, so the graphical load shouldn't be too heavy until you get to very extensive maps (release quality) and even then there are options like max render range you can adjust along with hiding certain groups of stuff you don't need visible at the time. However it can easily become RAM weighty (I've seen it at 2 GB) if you've used/viewed lots of materials or models during the session.

In my experience if you don't use the proprietary drivers for your graphic cards there will be issues. Otherwise feel free to test it.

I've run hammer on linux before. It worked well, a little glitchy with the window management in the app, and I can't remember how well the model/ texture browser was working. I haven't launched it since the sdk update, however, and I'm not sure how you should go about getting that to work.
I use an Nvidia card (560ti) with the proprietary drivers.
The major drawback is that compile times are a heck of a lot longer in wine. A super simple map that would have taken maybe 3 seconds to compile on windows was taking about a minute and a half to compile through wine. I'll post here again if I get the sdk update hammer working.

I got the steam pipe sdk working!
I used playonlinux (Download) to manage wine for me, along with an updated system wine, 1.5.31. If you are using ubuntu you will need to add a wine ppa to get this version of wine. Launchpad wine ppa
I installed steam with playonlinux and then re downloaded tf2. I had some problems trying to share the data files with my ntfs formatted windows drive, so I would use a ext4 formatted drive only.
After the game is installed hammer can be found under common/teamfortress2/bin. I launched hammer.exe with system wine-1.5.31.
As for settings I had the window manager manage the windows, but not decorate them. Running the program under a virtual desktop helped some of the graphical bugs, but it made the entity property window appear under the editor. :/ 1.5.31 worked all right, I'm not sure if another version would work better.
I don't think you can have wine hammer launch system native tf2 binaries, so I would just leave tf2 open on linux, and have hammer place the compiled bsps in your linux tf2's maps folder. This option can be changed in the options menu of hammer under build programs.
Compile times don't seem that bad for the small maps I compiled to test it, but I would assume that they are taking a large hit under wine. I'm not sure if wine will make the compiler produce errors, but I wouldn't be super surprised if it did.
Overall the program under wine seems all right, but there are some graphical problems relating to the views. These go away when you mouse over them or use them, but they make the editor feel a lot slower because the views don't update right when you put a new thing down, and need to be moved around a bit to display correctly.
I'll need some more time to test boojum's pack with wine hammer; I'm not even sure it is updated for steam pipe yet.

Having some trouble getting sourceSDK to fine tf2's gameinfo.txt I point it at C:/Program Files/Steam/SteamApps/common/Team Fortress 2/tf rather than the default steamapps/smyther/team fortress 2/tf but to no avail.

Edit: Oh, I've already ran tf2, and found gameinfo.txt

Edit: Whut. OK now it works, just be trying it 3 more times without changing anything. Oh well.

Edit: Tried to download and load freight, but attemting to open it brings a "file does not exist" message, but I don't think this is linux-specific territory now.

I use PlayOnLinux to manage Wine for me, I run Kubuntu 13.10 and both Steam on Wine and Steam for Linux have no noticeable problems.

hammer.exe runs pretty smoothly...until I edit entities. Then KWin (KDE window manager) crashes, crashes, crashes, and fucking crashes.

You can use either WINE or PlayOnLinux to insall Windows version of Steam, then use Half-Life SDK/Source SDK Hammer Editor/Portal 2 Authoring Tools Hammer Editor

IMPORTANT: I have tested ONLY, yes I mean it, ONLY Half-Life SDK's Hammer Editor. You can test Portal 2 Authoring tools for Y-O-U-R-S-E-L-F. I will not do tests with it. I will go test Source SDK Now. :closedeyes: