Lesswrong has plenty of tags; they are not organised well or easy to browse.

By creating a list of common tags or master tags (class/type tags); (and showing them on the page where article writing happens) We can help people classify their efforts. It's great to share a link of something found elsewhere on LW; but someone not interested in seeing linkposts cannot currently filter out link-posts from their view. They can choose not to click on them but I would much prefer a LW where I can opt-out of seeing posts on certain topics (easy example: politics).

Also if we show tags on the sidebar it will be easier to get a feel for what lesswrong is about (or filter what is available on lw) than say; reading the first 3 posts in discussion.