Sample code for blog post on exporting Queue members as Excel

QueueMembersController.cls

public class QueueMembersController {

    // selected queue whose members to view
    public ID queueId { get; set; }

    // provide queue name to show on page
    public Group selectedQueue {
        get {
            return [
                SELECT
                    id, name
                FROM
                    Group
                WHERE
                    id = :queueId
            ];
        }
    }

    // list of all active queue members
    public List<User> queueMembers {
        get {
            return [
                SELECT
                    id, firstName, lastName, alias, username, email, userRole.name, profile.name
                FROM
                    User
                WHERE
                    id IN ( SELECT userOrGroupId FROM GroupMember WHERE groupId = :queueId )
                    AND
                    isActive = true
            ];
        }
    }

    /**
     * Controller
     */
    public QueueMembersController() {
        queueId = ApexPages.currentPage().getParameters().get('queueId');
    }

    public PageReference refresh() {
        return null;
    }

    // picklist of queues whose members to view
    public List<SelectOption> getQueueOptions() {

        List<SelectOption> options = new List<SelectOption>();

        options.add( new SelectOption( '', '- Select -' ) );
        for ( Group grp : [
            SELECT
                id, name
            FROM
                Group
            WHERE
                type = 'Queue'
           ORDER BY
               name
        ] ) {
            options.add( new SelectOption( grp.id, grp.name ) );
        }

        return options;
    }

}

QueueMembersController.html

<apex:page controller="QueueMembersController" title="Queue Members" sidebar="false" docType="html-5.0">

    <apex:form id="mainForm">

        <apex:pageBlock id="mainPageBlock" title="Queue Members">

            <apex:pageMessages />

            <apex:pageBlockButtons>

                <apex:commandButton value="Export Details"
                                    onclick="window.open('{!URLFOR($Page.QueueMembersExcelPage, null, [ queueId = queueId ])}');"
                                    rendered="{!(queueId != null)}"/>

                <apex:commandButton value="Manage Queue"
                                    onclick="window.open('{!URLFOR("/p/own/Queue/d", null, [ id= queueId, setupid = "Queues" ])}');"
                                    rendered="{!(queueId != null)}"/>

            </apex:pageBlockButtons>

            <apex:pageBlockSection>

                <apex:pageBlockSectionItem>
                    <b>Queue:</b>
                    <apex:selectList value="{!queueId}" size="1">
                        <apex:selectOptions value="{!queueOptions}"/>
                        <apex:actionSupport event="onchange" action="{!refresh}" reRender="mainForm"/>
                    </apex:selectList>
                </apex:pageBlockSectionItem>

            </apex:pageBlockSection>

            <apex:variable var="rowCounter" value="1"/>
            <apex:pageBlockTable value="{!queueMembers}" var="user" rendered="{!(queueId != null)}">

                <apex:column headerValue="#">
                    <apex:outputText value="{!rowCounter}"/>.
                    <apex:variable var="rowCounter" value="{!VALUE(rowCounter) + 1}"/>
                </apex:column>

                <apex:column headerValue="Name">
                    <apex:outputLink value="/{!user.id}">
                        <apex:outputText value="{0} {1}">
                            <apex:param value="{!user.firstName}"/>
                            <apex:param value="{!user.lastName}"/>
                        </apex:outputText>
                    </apex:outputLink>
                </apex:column>

                <apex:column value="{!user.alias}"/>
                <apex:column value="{!user.username}"/>
                <apex:column value="{!user.email}"/>
                <apex:column value="{!user.userRole.name}" headerValue="Role"/>
                <apex:column value="{!user.profile.name}" headerValue="Profile"/>

            </apex:pageBlockTable>

        </apex:pageBlock>

    </apex:form>

</apex:page>

QueueMembersExcelPage.html

<!--
	How to create excel file in visualforce.
	http://help.salesforce.com/apex/HTViewSolution?id=000003176&language=en_US
 -->
<apex:page controller="QueueMembersController" contentType="application/vnd.ms-excel#QueueMembersExport.xls" cache="true">
    <apex:pageBlock >
        <apex:pageBlockTable value="{!queueMembers}" var="user">
            <apex:column headerValue="Queue" value="{!selectedQueue.name}"/>
            <apex:column value="{!user.firstName}"/>
            <apex:column value="{!user.lastName}"/>
            <apex:column value="{!user.alias}"/>
            <apex:column value="{!user.username}"/>
            <apex:column value="{!user.email}"/>
            <apex:column value="{!user.userRole.name}" headerValue="Role"/>
            <apex:column value="{!user.profile.name}" headerValue="Profile"/>
        </apex:pageBlockTable>
    </apex:pageBlock>
</apex:page>