This is Wikipedia's definition of a Blog:
"A blog (a portmanteau of web log) is a website where entries are written in chronological order and commonly displayed in reverse chronological order. "Blog" can also be used as a verb, meaning to maintain or add content to a blog.
Many blogs provide commentary or news on a particular subject; others function as more personal online diaries. A typical blog combines text, images, and links to other blogs, web pages, and other media related to its topic. The ability for readers to leave comments in an interactive format is an important part of many blogs. Most blogs are primarily textual, although some focus on art (artlog), photographs (photoblog), sketchblog, videos (vlog), music (MP3 blog), audio (podcasting) and are part of a wider network of social media. Micro blogging is another type of blogging which consists of blogs with very short posts."
Well that is kind of clinical description of a blog; from a internet marketing perspective blogging has become an important component of the entrepreneurs's web promotion toolset. Ok, now you know what a blog is let's provide some resources for those of you who already have a blog or are considering the creation of one. Happy blogging!