"Related Posts" is one of the most useful plugins for encouraging surfers to stay on your site. The author's site has been offline for a while now, but I just found another location for the download:
http://wasabi.pbwiki.com/Related%20Entries
And since I'm writing again, I may as well throw in a couple of other notes, the first about Ultimate Tag Warrior...
When WP 2.1 came along, it marked some significant changes in data structure, with which UTW was none to happy. Both scripts then went a couple of versions which didn't cooperate. However, I just updated my tutorial site and I have WP 2.1.3 running quite happily alongside UTW 3.14159265, so if you have run into any problems in the last few months, that combination should resolve them.
Hopefully people
validate their sites. Depending on your doctype, if you use the "Chicklet Creator" plugin I mentioned above, you might find the author has coded some of the image attributes in a way which throws validation errors. It is perfectly okay to go into his plugin file and modify the codes to clear such errors. The file is not large and the fixes are easy to figure out and apply.