I didn't understand the solution either. I resorted to creating my own session custom object and having the controllers update and retrieve data from this. I passed my custom session Id around in the queryString which told me which session to load up. Create your own timeout functions and it should work like cookieless sessions in other technologies.

I'm not sure a shared controller would work unless the whole of the session in serialised and stored in the viewstate of the visualforce page and reloaded when the next page is reached. (Umm no, that wouldn't work either as any 'get' (standard hyperlinks) wouldn't get this data... It'd only be valid for page postbacks (in the .net world anyway) - ignore this)

Perhaps SF could provide more information???

Thanks Richie :)

That was actually my last resort, I guess I'll have to do something similar. Any chance of sharing your session manager? 

sorry - no can do. Work was done for a paying client who now owns the IP. 

Good luck! 

I'll try to describe my use case as clearly as possible there may be a better way to achieve what I'm attempting to do.

On my site I have various different kinds of content stored in custom objects displayed by various visualforce pages. I need to be able to keep track of which visualforce pages and which content the users have been too to dynamically generate the bread crumbs for the site. Ideally the bread crumbs would be a component that I coud include in any of the templates or compositions.

The work around I'm using now is to have a bread crumb custom object and use javascript to store the initial session_id in a cookie and then use an ajax call to load the bread crumbs based on the cookie.

I've just started the implementation so it's not completed yet but it will work. It's just a really bad hack. I would like to avoid having every url in the site be an action call. Here's the code so far:

//Javascript
$(document).ready(function(){

//Bread Crumb Code
if(!$.cookies.get('guest_session')) {
$.cookies.set('guest_session', '{!$Api.Session_ID}', {expires: 1});
}

AddBreadCrumb($.cookies.get('guest_session'));
}

//Apex
public PageReference AddBreadCrumb() {

this.session_id = System.currentPageReference().getParameters().get('session_id');
this.bread_crumbs = [SELECT Id, Location__c, Page_Name__c, Order__c FROM Bread_Crumb__c WHERE Session_Id__c =: this.session_id ORDER BY Order__c ASC];

Bread_Crumb__c current = new Bread_Crumb__c(Session_Id__c = this.session_id, Location__c = this.CurrentPageUrl, Page_Name__c = this.CurrentPageName, Order__c = this.bread_crumbs.size());
insert current;

return null;
}

//Visualforce
<apex:form >
<apex:actionFunction name="AddBreadCrumb" action="{!AddBreadCrumb}" reRender="bread_crumbs" />
<apex:outputPanel id="bread_crumbs">
<div class="bread-crumbs">
<apex:repeat value="{!bread_crumbs}" var="bread_crumb" >
<a href="{!bread_crumb.Location__c}"><apex:outputText value="{!bread_crumb.Page_Name__c}" /></a> >
</apex:repeat>
</div>
</apex:outputPanel>
</apex:form>

 This idea also has some details about why we might want to be able to access the session:

I understand, thanks for spelling it out, this appears to be a hard problem.

your solution may to assume that the sessionID is different or usefull , i did a quick test using this page

<apex:page > {!$Api.Session_ID} </apex:page>

i then made it public on a site, and hit it from two different computers. 

I get the same session id for both.

this is because the Guest User is the user for every page delivered by the server, and all users of your site would have the same session id at the same time.  

i'll give it some thought, no ideas spring up yet.