How does one write a combat scene? That's a complicated question.

Barry Eisler, author of the Rain series, has what I considered a very realistic approach to combat scenes. Rain, his main character, will even compare his combat experience, in the books, to unrealistic Hollywood scenes. (Do not bring a knife to a gun fight.)

Matthew Reilly, author of the Scarecrow/Shane Shofield series, is perhaps an example of how not to write combat scenes. His books are entertaining, but they lack realism and research. Temple, one of his stand alone novels, like all of of his books, is an example of writing wall-to-wall action. Its not very realistic, however. Good read, though. Hell Island, is a wonderful example of not researching one's topic, particularly in regards to Gorillas and apes in general. It is entertaining, though, as one would watch a horribly unrealistic action movie, such as Stalone/Russel's Tango and Cash.

For Writers: How to write sword-fight scenes: A wordy article that talks about sword-fights in literature. It has some good ideas.
How to Write a Great Combat Scene - Advise for Fantasy Writers: Basic information. No examples. Link to additional articles.
How to Write a Fight Scene: This short piece goes into avoiding repetitive word usage.
How to Write Fight Scenes: A short, simplistic introduction. Informative. (Scroll past the ads. They're annoying.)
Marilynn Byerly - Creating Fight Scenes and Battles: Information about combat realism, including character limitations. (Includes why Xena, for example, is not realistic.)

List of Martial Arts (wikipedia)
Types of Martial Arts
Types of Martial Arts: covers a lot of information on who should use what type of martial arts
Top 10 Martial Arts

What is the best type of Martial Arts?

Martial Arts
Historical European martial arts

Bare-knuckle boxing
Russian fist fighting