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.
With regards to user-agent, that is entirely up to the creator of the application. See this semi tongue-in-cheek history of user-agent. In summary, there really isn't a canonical set of values. Microsoft based user-agents may change based on software installed on the local machine (version of .NET framework, etc).
Did you try the RFC? It has all that information.
Actually, when searching for information on any protocol or standard, try to search for the RFC first.
Cheers.
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.
The list of HTTP headers is easily available on the W3 website:
PConroy also linked to the wikipedia page, which is more concise, and a little easier formatted:
However, the "User-Agent" header is a bad example, since there's no set response; the user-agent string is decided by the client so it can literally be anything. There's a very comprehensive List of User Agents available, but it's not necessarily going to cover any possible option, since even some toolbars and applications can modify the user-agent for Internet Explorer or other browsers.
The chipmunk book from O'Reilly is good as is Chris Shiflett's HTTP reference.
Oh, whoops, it's not a chipmunk. It's a thirteen-lined ground squirrel.