I'm interested in tagging some of my site content (probably via a backend?) and then creating lists of "related content" that I can append to pages of existing content. For example if I have a page about Helicopters and a page about Hot Air Balloons both might be tagged "air travel" and as such on the bottom of each page a "related items" section would point to each other. Anyone know of any such backend tool? Could be PHP or ASP.