Blogs tend to come in two varieties - those that are simply online diaries and those which are based on a certain topic...and no, you don't have to be a computer nerd or lack a social life to have one.
The 'diary' type is usually the work of an individual and doesn't pretend to be anything other than an informal journal of events in someone's life. Those who complain that these blogs are of no interest to most people are missing the point - they're not meant to be! They are primarily aimed at friends and family of the blogger to keep up with their news. You can normally restrict who views such a blog to those you invite, but many people don't bother to do this.
The other, less well known type is usually (but not always) more formal and structured and may be the work of an individual or a team representing some company or focus group. These may be on politics, sport, travel, or any particular topic you fancy. They are normally aimed at a larger audience, so their reputation depends on a fairly professional approach and regular updates.
There are many sites that can help you build a blog easily and for free. For example:
blog.com
blogger.com
myblogsite.com