Yeah, this has been a huge source of frustration for me, a rare liberal civil engineer. A lot of my coworkers listen to Rush all day long. Luckily, I’m now sitting on the other side of the office with the planners and the biologists.
IT people and computer techs tend to be fairly libertarian, IME, though a lot of us aren’t anything like active in politics.
Newspaper journalists tend to be fairly liberal (but the good ones don’t let it show in their news stories), while the owners of newspapers, and some editors, are more conservative, at least in my experience. Newspaper columnists, of course, run the gamut.
General politics makes for interesting office politics in a newspaper environment. I worked on a staff of very liberal people at a paper that happened to be owned by a conservative – imagine our joy in typesetting, editing, and printing the paper’s endorsement of George Bush the Elder in 1992.
Well, The Trees was sort of Libertarian, but…oh. Nevermind. (I can also imagine civil engineers liking the band, too.)
All the sign shop owners I’ve known have been Republicans, even the lesbian. In general I see a strong tendency towards small business owners to be convinced that the Right is on their side, even though the legislation that they actually pass is much more likely to help huge multi-national corporations.
Scientists at a biotechnology company: My coworkers cover a range but there are probably more who would describe themselves as left wing than right wing, especially on lifestyle issues, probably less so on fiscal/economic issues.
On the other hand my longtime supervisor is politically very conservative, and the former CEO of my company is a fairly prominent Republican. I assume the higher management echelons tend to be more conservative on tax and regulation issues.
My wife is from a financial services background and I know that industry tend to be more Republican types.
Landscapers tend to be right wing, except for those of us who specialize in organic/native plants. Naturalists tend to be heavily left-leaning. Obedience instructors don’t care for politics outside of the AKC!
The bulk of the computer programmers I have worked with have been conservative, with a libertarian bent. Unusually for my experience, where I work now most of the programmers (including me) are liberal, with a libertarian bent.
Yeah, we tend to lean to the right as a group.
Well, consider the alternative. The Left is dominated by ivory-tower types and environmentalists, who tend to be much less accomodating to business’ interests.
Actuaries on the whole tend to be conservative, although there are a few left-leaning ones about.
My fellow computer science undergrads in college were disproportionately libertarian. I think the highly technical fields with tenuous connections to social realitiy (e.g. computer science) tend to attract the libertarians, which makes sense, since libertarians inhabit a fantasy world in which human beings behave like computer programs. 
I’m a died-in-the-wool pinko commie liberal bastard, for what it’s worth.
The ones I work with (in the military-industrial complex at that) generally fall into the social-liberal, fiscal-conservative American archetype now generally lumped under the name “liberal”. Could be a regional thing, though, and there are a few evangelicals around.