So I have an interesting issue that seems to only manifest on sites/customer portal. As I'm only using portal for authentication and this code is all being run by custom controllers under sites this seemed like the appropriate place to post it.

I have a custom controller that looks something like this: 

public without sharing class Controller {

[irrelevant code cut out]

public List<Service_Availability_Link__c> getServiceList(){
List<Service_Availability_Link__c> ServiceList;
try {

ServiceList = [Select Name, Service__r.Name From Service_Availability_Link__c r
where Department__c = :myContact.Department__c and Service__c != null];

} catch (Exception e) {
System.debug('******Cought an exception! '+e);
}
System.debug('**# Service list looks something like this: '+ServiceList[0].Service__r.Name);
return ServiceList;
}

 And here's a especially simple VF page that I made to help illustrate the issue:

<apex:page controller="Controller" showHeader="false">
<apex:repeat value="{!serviceList}" var="s">
<apex:outputText >Data: {!s.Service__r.Name}<br /></apex:outputText>
</apex:repeat>
</apex:page>

This is the interesting part, the custom controller is running without sharing (to help debug this issue, I plan to enable sharing rules), and when I turn on debug logs I can see the "System.debug('**# Service list looks something like this: '+ServiceList[0].Service__r.Name);"  statement printing the data I want, but the data is not accessible on the VF page.

Here's what I get when I load the VF page.

In full salesforce (not using sites):

Data: Salesforce Account

Data: CEO Laptop Service

Data: New Laptop

Data: InSite Monitoring Seat License

 And when I run it under sites with a customer portal user I get this output:

Data:

Data:

Data:

Data:

Even stranger, if I change the VF page to print  {!s.Name} instead of {!s.Service__r.Name} it prints data (just not the data I want)! The issue seems to be only with traversing object relationships, and from the debugging statements I can see the data is being pulled correctly.

Is this a bug in visualforce under sites? I can't figure out any reason why it would behave like this.