apex:inputFile

<!-- Upload a file and put it in your personal documents folder-->

<!-- Page: -->
<apex:page standardController="Document" extensions="documentExt">
    <apex:messages />
    <apex:form id="theForm">
      <apex:pageBlock>
          <apex:pageBlockSection>
            <apex:inputFile value="{!document.body}" filename="{!document.name}"/>
            <apex:commandButton value="Save" action="{!save}"/>
          </apex:pageBlockSection>
       </apex:pageBlock>
    </apex:form>
</apex:page>
                
/*** Controller ***/
public class documentExt {
    public documentExt(ApexPages.StandardController controller) {
        Document d = (Document) controller.getRecord();
        d.folderid = UserInfo.getUserId(); //this puts it in My Personal Documents
    }                 
}