Though not dedicated exclusively towards sales careers, Glassdoor provides information about what it's like to work for a specific company, including approximate salaries, working conditions, and opinions on senior management.
Glassdoor certainly doesn't have information on every company in the world, but you'll be surprised at just how many companies have at least some content about them on the site.
A word of caution: Many of the company reviews are written by ex-employees, some of whom may have an axe (or two) to grind with their old employer.
You'll also read plenty of employer reviews by current employees. While this may not be the best way to research a company you may want to join, it can be a very useful resource.
Selling Power is one of the first magazines that many new sales reps get to know. It is an excellent resource for those in sales and frequently has articles on selling skills, sales careers, best companies to sell for and general business information.
However, as you may know, the magazine industry is struggling due to more and more people choosing to get their reading material online. Understanding this, traditional paper-based magazines are making their online content a top priority. Selling Power is no exception, and it is attempting to monetize its online presence. The website is a combination of free and fee, meaning that without a membership, you won't have access to all the site's content. However, there is enough free content for you to decide for yourself whether or not it's worth the investment to subscribe.
Don't make the mistake of thinking that Entrepreneur magazine and their associated website is only for entrepreneurs. The site (and magazine) is for anyone in the business world. While you will find a lot of content geared towards those interested in starting their own business, there is a ton of good info to help you increase your sales skills and to advance your business position, no matter your industry.
In general, the articles you'll find on the website are geared for bigger ticket sales and more tenured reps. But don't let that stop you from reading any article that interests you. It's a growth tool to read about sales careers that are more advanced than your current position.
Some of the absolute best articles on sales and sales careers that I've read were posted on Forbes.com. Like Entrepreneur.com, Forbes.com is not specifically geared for sales professionals but has a ton of sale-centric content.
Visit the site, search for "sales" and get ready for a whole lot of suggested articles.
The Top Websites for Sales Professionals
The Internet is an incredibly powerful resource. Like any resource, it can be used for good purposes or for reasons that are not so good. The same is true for sites dedicated for sales professionals: Some are good and some, well, let's just say a sales professional's time would be better spent elsewhere.
For sales professionals especially, time is money, and any time spent on research should be done so using good information from reliable resources. Here is a list of website that have proven themselves valuable for sales professionals that need to do research with a variety of goals in mind.