I'm looking for all the current standard header values a web server would generally receive. An example would be things like "what will the header look like when coming from a Mac running OS X Leopard and Camino installed?" or "what will the header look like when coming from Fedora 9 running Firefox 3.0.1 versus SuSe running Konqueror?"
PConroy gave an example from JQuery tending towards what I'm looking for. What I want though are the actual example headers.
There is no set-in-stone list of user agent values. You can find lengthy lists (such as this one used by the JQuery browser plugin).
Regarding other HTTP Headers, this wikipedia article is a good place to start.