Windows/Mac/Linux: YouTube is a bloated site with a lot going on. If you really want to simplify using it, MPS-YouTube is a YouTube player that works entirely from the command line.
With MPS-YouTube you can search for audio and video, import YouTube playlists, match albums, download files, and create new playlists. If you use YouTube as a music player, MPS-YouTube is great because it's lightweight and out of the way. It's surprisingly powerful too, so even if you just want to keep yourself off of the YouTube site it does just about everything you need it to.