With our upgraded message boards, you now have the option to tag posts. These tags work just like tags on a blog. When composing a message, there is a small box to the right where you can enter tags like "recipes" or "tips" separated by commas. To find your tags, search using the search box, or find your list of tags under Edit My Preferences, then Tagging.
I've tagged the tips here on Tour Guide with the tag "tips" so you can find them easily.