You can now browse games by popular tags such as "Steam Trading Cards" or "difficult," or by tags recommended to you based on your play and purchase history. Steam Tags are multi-lingual, too – so you can add tags in English, Russian, Danish and more. Sorry, it doesn't look like Steam supports Klingon or Elvish tags.
The implementation of Steam Tags follows last week's addition of a Recently Updated section providing an at-a-glance view of games that have been patched or received new content. Valve also plans to introduce a Steam Music beta soon, which will allow users to listen to local library files through the Steam client while playing their games.