It looks like many seniors have discovered the joys of blogging just as I have. Recent numbers indicate that 22% of Americans over the age of 65 (about 8 milllion seniors) use the Internet. And 3% of the online seniors have created a a blog.
By the way, a "blog" is simply a website that is updated much more frequently than a traditional website. A typical website could go months and even years without being changed while some blogs are updated daily and sometimes multiple times per day. Many blogs serve as online journals (the modern equivalent of a traditional diary) that the public can read and occassionally offer feedback.
Seniors have joined the world of "bloggers" (those who create and maintain blogs) in order to keep their minds sharp, stay current on news events, meet people from around the world online and just share experiences and stories on the Internet.
There is an interesting article on this senior phenomenon at MSNBC. And this about.com article can be helpful if you are interested in starting a blog yourself!