Need help with your tags? Tagyu, developed by Adam Kasley, is a tagging service that will help you find tag suggestions.
Simply copy and paste part of your blog entry into the textarea form on the page or paste the URL of the published post and click submit and it should generate a list of tag suggestions. It is also used by The Ultimate Tag Warrior WordPress Plugin for keyword suggestions.
It’s still new and I find that it is pretty good most of the time to come up with good tag recommendations, but a lot of time it comes up with odd suggestions. I’m sure as it grows and improves, it will become really useful for determining which tags you should consider when tagging your posts.