I need to store a single numerical value in the admin for use in my templates. What is the best way to do this. I've reviewed Accessories, Extensions and Modules but can't seem to find something that has the simplicity of setting up the admin area and the ease of using it on the front end template.
Set up a Global Variable with the value you need. Then you can access the value from within a template simply by including the Global Variable name (within curly brackets) within your templates - e.g.
In EE2, Global Variables are set via the Control Panel - go to Design / Templates / Global Variables to do this. More info here