I have a websites where i write about companies. Is it legal to put their logos on that site (e.g. stock information on coca-cola, can I put a logo in there)?
If you have permission, from them then you can, otherwise no. Im not sure but their name is copyrighted, so you may even have to ask them for permission to use their brand name, in your article.
With permission they(you) can, as your using their logo in your articles, that alone is attracting vistors and the logo is the brand of that company and its not yours to use. Same as any picture/photo/graphics, you need to own the copyright to re-produce the image how ever you like with rules by the company whom created the image, but it becomes more of a problem if that image show off a big co-operations. For example a cheap soda drink, no ones going to be interested in the article but there is going to be more interest in a popular soda drink like pepsi.
There is a certain amount of fair use that comes in to play in the type of situation.. They are not trying to sell the product (pepsi for example), they are not selling a competitive product, and they are not trying to deceive readers i to thinking that they are that company.. In a review situation the logo, screenshots/pictures, even short audio/video clips are all fair use.. Many companies even have "press" versions of their logos for just this type of scenario.. I published a review magazine for several years.. Been here.. Done this.. They are just happy to be getting the press/reviews..
You should still always get permisson off the owner though, as your dont want to be hit with copyright laws.
Please see Wikipedia's fair use page at http://en.wikipedia.org/wiki/Fair_use to get an idea of what is acceptable. Also to be safe, add a disclaimer in your website footer on every page, something like"WebTechnocrat.com is a trade mark of WebTechnocrat. All other logo and trademarks are copyright their respective owners, and WebTechnocrat.com is not affiliated with them in any manner." Also you can put a DMCA policy and contact link on your website, this way there is an official procedure if someone claims that you are infringing copyright.