Cascading Style Sheets menus are becoming a very popular replacement to the traditional methods (e.g., tables with hyperlinks and buttons).
There are several different websites out there that I have used personally for my business and personal websites. A good source is http://www.dynamicdrive.com/style/ or http://cssmenumaker.com/
Another source, which has free premade CSS website templates is http://www.openwebdesign.org/ where you can use the entire website, or just copy and paste the menu portion into your existing web site html code (be sure to give the designer a credit at the bottom of your web page though!)
Now, in order to make it so you don't have to copy and paste the CSS code into every new web page you will need to create an include file with the CSS code embedded within it. If you don't know how to do this, I recommend going to a site such as http://www.hardcoder.com/scripting/php/include_files.php#why
You will need to prepare to learn a bit about PHP (hypertext preprocessor) server-scripting. There are plenty of services out there that can help you learn about that, such as http://www.php.net
Otherwise, your other option is to copy one of your preexisting web pages with the CSS code in it, rename it as "template.html" and use this to make new pages without having to worry about recreating a new page every single time from scratch.
Good luck and have fun!