I work for a high traffic content website that offers news, photos & videos (amongst other things). One thing we struggle with is perfecting our "related items" module. If you are viewing a video, we show a list of 5 related videos. This applies to blog posts, articles, etc... Our team does a good job tagging the content w/ keywords as well as relating it to an appropriate category, and associating it with items of other content types, but whatever mechanism we try when displaying "related content" it's never close to 100% accurate. 

Are there any tried and true ways to get fairly accurate results based on the tagged keyword, title, or category name? Our site is .net (c#) and uses SQL 2005. Let me know if you need me to elaborate. 

Thanks!