I just use the free Classic Shell. I used it with Win 8 to start with, and still use it with Win 8.1 Update [1]
Get it here:
http://www.classicshell.net/
Chances are, the default settings will work just fine for you, where you have a more traditional start menu button and programs menu, and boot directly into the desktop instead of the new Metro Style start screen, etc.
But, if you don't like the defaults for some odd reason, it's features are highly customizable to suit individual tastes (even including the exact start menu style you want to see). Available Customization is one of it's strong points.
Again, it's also free.
But, there are some commercial options available, too. For example, Start8 is another popular choice that only costs $4.99 for personal use:
Product info:
http://www.stardock.com/products/start8/
Pricing:
http://www.stardock.com/products/start8/download.asp
But, I've never bothered to try Start8, since the free Classic Shell works just fine for me.