Being a Slytherin in modern society puts a major stigma against anything you might want to do. So here are 10 majors that will take you on very Slytherin life paths, without (much) of an evil stigma.
Business
Its part of the nature of Slytherins to want to be in charge of powerful things and what better way to do that than to be the CEO of a large company?
Chemistry
Going straight up book for this one. Potions = Chemistry
Political Science
Politics is right up the average Slytherin's alley. Combining the ability to advance and standing for a belief system creates an irresistible combination for any power hungry person.
Communications
Communications can lead to a lot of diverse things, but mainly jobs in the media. Working in the media is great because it is an easy way to be able to twist an agenda to point out or ignore certain plots. Very Slytherin.
Law
Being able to use the law for one's own gain is probably one of the most Slytherin things I can think of. No matter what a Slytherin does, they always come out on top.
Sociology
Sociology is the study of how people act in groups. A cunning Slytherin will know that group mentality is important to knowing how to control people.
History
One of the core things about Slytherins is that they don't want to make the same mistakes twice. And how does one learn from their mistakes? By studying History. A history major could easily lead to teaching history which is a great way to shape new minds into believing something.
Theatre
A Slytherin always needs to be ready to act and lie at a moments notice. Whether it's getting a lead or covering up a plot, the theater is the place to be.
Physics
Just imagine being so devoted to doing just one thing that most people say is impossible, like wanting to fly. The only way to accomplish this goal would be to learn every about the supposed "reasons" you can't and changing them. Changing the laws of physics quite ambitious.
Psychology
To know how a person thinks and be able to predict it can and will lead to a better working knowledge of said person. Of course, all knowledge gained should only be used for the greater good.
Naturally, anyone who considers themselves a Slytherin probably already has some indication of what they want. Even if it is as broad as 'nothing with blood', like it is for me. And of course, this is by no means a comprehensive list. I'm sure that any Slytherin has the ability to make any major suit their needs.