Meerkat can be easily customized to suit you needs. You can allow users to close the panel or automatically disable the panel until browser session has ended or for a set amount of days. You can also customize other options such as fade or slide; animation speed; background colors; height and its panel position.
Developed by Jarod Taylor; Meerkat jQuery Plugin is available for download under MIT License. You can find further information, demos & download on Meerkat Website.