Export Data To CSV

public class exportCSVController {

    public List> myList {get;set;}
    
    public exportCSVController() {
        myList = new List>();
        List temp = new List();
        
        for(Integer i = 0; i < 2500; i++){
            if(temp.size() < 1000){
                myClass m = new myClass();
                m.val1 = 'val1 ' + i;
                m.val2 = 'val2 ' + i;
                temp.add(m);
            }
            else{
                myList.add(temp);
                temp = new List();
                myClass m = new myClass();
                m.val1 = 'val1 ' + i;
                m.val2 = 'val2 ' + i;
                temp.add(m);
            }
        }
        myList.add(temp);
    }
    

    public class myClass{
        public string val1 {get;set;}
        public string val2 {get;set;}
    }
}

<apex:page controller="exportCSVController" cache="true" contentType="text/csv#Export.csv" language="en-US">
    "Col A","Col B"
    <apex:repeat value="{!myList}" var="a">
        <apex:repeat value="{!a}" var="asub">
        "{!asub.val1}","{!asub.val2}"
        </apex:repeat>
    </apex:repeat>
</apex:page>

Reference: http://boards.developerforce.com/t5/Apex-Code-Development/How-to-export-data-to-CSV-file-using-Apex/td-p/166567/page/2