Este código es para enviar mensajes a alguien en Skype pero no sé cómo configurarlohttps://play.google.com/store/apps/details?id=com.skype.raider en caso de que no tuviera Skype.

skypename.setOnClickListener(new OnClickListener() {
                  @Override
                   public void onClick(View v) {
                      Uri skypeUri = Uri.parse("skype:username?chat");
                      Intent myIntent = new Intent(Intent.ACTION_VIEW, skypeUri);
                      myIntent.setComponent(new ComponentName("com.skype.raider", "com.skype.raider.Main"));
                      myIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                      startActivity(myIntent); 
                      }
                  });

Código agregado ................................................ .................................................. .

skypename.setOnClickListener(new OnClickListener() {
   @Override
     public void onClick(View v) {
      if (!isSkypeClientInstalled(activity)) {
        Context activity;
        goToMarket(activity);
        return;
     } else{ 
       Uri skypeUri = Uri.parse("skype:username?chat");
       Intent myIntent = new Intent(Intent.ACTION_VIEW, skypeUri);
       myIntent.setComponent(new ComponentName("com.skype.raider", "com.skype.raider.Main"));
       myIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
       startActivity(myIntent); 
       }

public void goToMarket(Context myContext) {
   Activity activity;
  try {
      activity.startActivity(new Intent(Intent.ACTION_VIEW, Uri.parse("market://details?id=" + "com.skype.raider")));
                    } catch (android.content.ActivityNotFoundException anfe) {
                         activity. startActivity(new Intent(Intent.ACTION_VIEW, Uri.parse("http://play.google.com/store/apps/details?id=" + "com.skype.raider")));
                    }
                      return;
                     }
                public boolean isSkypeClientInstalled(Context myContext) {
                      PackageManager myPackageMgr = myContext.getPackageManager();
                      try {
                       myPackageMgr.getPackageInfo("com.skype.raider", PackageManager.GET_ACTIVITIES);
                      }
                      catch (PackageManager.NameNotFoundException e) {
                       return (false);
                      }
                      return (true);
                     });