Example of a JavaFX Pane which slides in and out on command.

slideout.css

/** file: slideout.css
    place in same directory as SlideOut.java */
.root  {
  -fx-background-color: cornsilk;
  -fx-font-size: 20;
  -fx-padding: 10;
}

.lyric-text {
  -fx-font-size: 20;
  -fx-fill: darkgreen;
  -fx-font-weight: bold;
  -fx-text-alignment: center;
}

.sidebar {
  -fx-padding: 10 10 10 10;
  -fx-background-insets: 0 10 0 0;
  -fx-border-insets: 0 10 0 0;
  -fx-background-color: linear-gradient(to bottom, derive(lavenderblush, -10%), derive(mistyrose, 10%));
  -fx-border-color: derive(mistyrose, -20%);
  -fx-border-width: 4;
}

/** icons from: http://www.customicondesign.com (free for non-commercial use). */
.hide-left {
  -fx-graphic: url('http://www.veryicon.com/icon/64/Business/Pretty%20Office%205/Hide%20left.png');
}
.show-right {
  -fx-graphic: url('http://www.veryicon.com/icon/64/Business/Pretty%20Office%205/Hide%20right.png');
}
.change-lyric {
  -fx-graphic: url('http://www.veryicon.com/icon/64/Business/Pretty%20Office%205/Go%20into.png');
}

SlideOut.java

import javafx.animation.*;
import javafx.application.Application;
import javafx.event.*;
import javafx.geometry.Pos;
import javafx.scene.*;
import javafx.scene.control.*;
import javafx.scene.layout.*;
import javafx.scene.text.Text;
import javafx.scene.web.WebView;
import javafx.stage.Stage;
import javafx.util.Duration;

/** Example of a sidebar that slides in and out of view */
public class SlideOut extends Application {
  private static final String[] lyrics = {
    "And in the end,\nthe love you take,\nis equal to\nthe love\nyou make.",
    "She came in through\nthe bathroom window\nprotected by\na silver\nspoon.",
    "I've got to admit\nit's getting better,\nA little better\nall the time."
  };

  private static final String[] locs = {
    "http://www.youtube.com/watch?v=osAA8q86COY&feature=player_detailpage#t=367s",
    "http://www.youtube.com/watch?v=IM2Ttov_zR0&feature=player_detailpage#t=30s",
    "http://www.youtube.com/watch?v=Jk0dBZ1meio&feature=player_detailpage#t=25s"
  };
  WebView webView;
  public static void main(String[] args) throws Exception { launch(args); }
  public void start(final Stage stage) throws Exception {
    stage.setTitle("Slide out YouTube demo");

    // create a WebView to show to the right of the SideBar.
    webView = new WebView();
    webView.setPrefSize(800, 600);

    // create a sidebar with some content in it.
    final Pane lyricPane = createSidebarContent();
    SideBar sidebar = new SideBar(250, lyricPane);
    VBox.setVgrow(lyricPane, Priority.ALWAYS);

    // layout the scene.
    final BorderPane layout = new BorderPane();
    Pane mainPane = VBoxBuilder.create().spacing(10)
      .children(
        sidebar.getControlButton(),
        webView
      ).build();
    layout.setLeft(sidebar);
    layout.setCenter(mainPane);

    // show the scene.
    Scene scene = new Scene(layout);
    scene.getStylesheets().add(getClass().getResource("slideout.css").toExternalForm());
    stage.setScene(scene);
    stage.show();
  }

  private BorderPane createSidebarContent() {// create some content to put in the sidebar.
    final Text lyric = new Text();
    lyric.getStyleClass().add("lyric-text");
    final Button changeLyric = new Button("New Song");
    changeLyric.getStyleClass().add("change-lyric");
    changeLyric.setMaxWidth(Double.MAX_VALUE);
    changeLyric.setOnAction(new EventHandler<ActionEvent>() {
      int lyricIndex = 0;
      @Override public void handle(ActionEvent actionEvent) {
        lyricIndex++;
        if (lyricIndex == lyrics.length) {
          lyricIndex = 0;
        }
        lyric.setText(lyrics[lyricIndex]);
        webView.getEngine().load(locs[lyricIndex]);
      }
    });
    changeLyric.fire();
    final BorderPane lyricPane = new BorderPane();
    lyricPane.setCenter(lyric);
    lyricPane.setBottom(changeLyric);
    return lyricPane;
  }

  /** Animates a node on and off screen to the left. */
  class SideBar extends VBox {
    /** @return a control button to hide and show the sidebar */
    public Button getControlButton() { return controlButton; }
    private final Button controlButton;

    /** creates a sidebar containing a vertical alignment of the given nodes */
    SideBar(final double expandedWidth, Node... nodes) {
      getStyleClass().add("sidebar");
      this.setPrefWidth(expandedWidth);
      this.setMinWidth(0);

      // create a bar to hide and show.
      setAlignment(Pos.CENTER);
      getChildren().addAll(nodes);

      // create a button to hide and show the sidebar.
      controlButton = new Button("Collapse");
      controlButton.getStyleClass().add("hide-left");

      // apply the animations when the button is pressed.
      controlButton.setOnAction(new EventHandler<ActionEvent>() {
        @Override public void handle(ActionEvent actionEvent) {
          // create an animation to hide sidebar.
          final Animation hideSidebar = new Transition() {
            { setCycleDuration(Duration.millis(250)); }
            protected void interpolate(double frac) {
              final double curWidth = expandedWidth * (1.0 - frac);
              setPrefWidth(curWidth);
              setTranslateX(-expandedWidth + curWidth);
            }
          };
          hideSidebar.onFinishedProperty().set(new EventHandler<ActionEvent>() {
            @Override public void handle(ActionEvent actionEvent) {
              setVisible(false);
              controlButton.setText("Show");
              controlButton.getStyleClass().remove("hide-left");
              controlButton.getStyleClass().add("show-right");
            }
          });
  
          // create an animation to show a sidebar.
          final Animation showSidebar = new Transition() {
            { setCycleDuration(Duration.millis(250)); }
            protected void interpolate(double frac) {
              final double curWidth = expandedWidth * frac;
              setPrefWidth(curWidth);
              setTranslateX(-expandedWidth + curWidth);
            }
          };
          showSidebar.onFinishedProperty().set(new EventHandler<ActionEvent>() {
            @Override public void handle(ActionEvent actionEvent) {
              controlButton.setText("Collapse");
              controlButton.getStyleClass().add("hide-left");
              controlButton.getStyleClass().remove("show-right");
            }
          });
  
          if (showSidebar.statusProperty().get() == Animation.Status.STOPPED && hideSidebar.statusProperty().get() == Animation.Status.STOPPED) {
            if (isVisible()) {
              hideSidebar.play();
            } else {
              setVisible(true);
              showSidebar.play();
            }
          }
        }
      });
    }
  }
  
}

Is is possible to have the WebView right of the Sidebar to expand if you hide the Sidebar and shrink if you show the Sidebar ?
I thought of an Event triggered by the Animation to translate the other View too.