Thanks Scott,
I see where you are going with your answer and appreciate the info as helps me see what's going on under the hood.
I probably didn't explain my situation so well which happens all too often when trying to abstract a problem. Basically I needed a way to link my product page to my shopping cart page so I could add products. The base URL to the shopping cart will be the same throughout the entire site. The products are managed externally so the links need to be formed dynamically with the product id.
I will only have one cart on my site, so I decided that the module settings looked like the easiest place to put the info. I added a module setting to hold the cart url. I used the UpdateModuleSetting() method so the setting can be shared anywhere I use my module.
This works okay but I really want to use a portal level setting so that if I create multiple modules that all need to point to the same shopping cart, you only need to adjust the setting in one location. I could do this by creating my own settings table but if I needed to do this, it might be easier and quicker just to set it in multiple locations.
I saw in the video where UpdateTabModuleSetting() connects a setting to a instance of a module and UpdateModuleSetting() updates a setting that is shared by all instances of a module. Is there an equivalent that is set at the portal level? I did a little poking around and saw that there is a PortalModuleBase() object that has a settings variable. Is this the key?