I recently discovered a site called squidoo.com where you can create your own "lens" or web page that focus on a given topic that you might have some knowledge. In addition, you can easily link to sites like eBay or Amazon with any related items for purchase. One other benefit is that you can generate revenue depending on how many clicks you can attract to your site. You can choose to donote the revenues to many worthy charities or keep it.  It is a win-win situation.
Here is a list of my current lens:

http://www.squidoo.com/lensmasters/jackclee

Currently, there are over 60,000 lens and more created each day.
You can also search for lens that may or may not exist.
Your lens will also be automatically catagorized by search engines such as google.

Have fun!!!

-Jack