I've got a situation where I want to have a master list at the top level of a Sharepoint site, and then allow the sub-sites to see the master list. I've tried working with Content Types, and either I'm slow and just can't get the concept, or it doesn't seem to apply.
Anyone have any luck?
It depends on what you mean by "see" the master list.
If you're writing code to access it, you can do that by getting an SPWeb object for the top level site and using its Lists property.
If you just want to display it on a web part page, you can do that with a Content Query Web Part.
If you want to use it in other lists somehow, that's a more involved question. You can definitely set up lookup columns to point to lists in other sites, but we've only done that via custom site and list definitions.
Also, if you want to reuse some text or HTML from your master list and you're using MOSS, the Reusable Content list in the site collection's top site is useful.
I heard some web parts can build relation between lists that are located on different sites. But it is new to seek sharping list relationbetween master-sites and sub-sites. I am not sure if this relation can be seen as cross-site, if positive then take a look at Sharepoint Cross-site Lookup. Otherwise for me your requirements is an "involved question" .
If you want to be able to have a lookup column, looking in another list at a higher level site. you can at the higher level site create a site column (under site settings) that is a lookup field to the socalled masterlist. Then on the list in a subsite, you can add a site column, then choose the site column you created earlier.