The Visualforce and Apex below is being used via an externally, anonymously accessible Force.com site.  The error text is:

Maximum view state size limit (128KB) exceeded. Actual view state size for this page was 149.953KB

I've been reading more than a few threads on file upload sizes and the state size, but most are old.  In fact, most claim you can do a 5MB upload, so I don't understand the problem, because, despite what I describe next, this error only shows up when I upload a file that's more than 100K or so.

Now, I do have a rather large object floating around in the state (on the order of one hundred fields, with many text areas and rich text areas of up to 4500 char limit).  This object is kept around because I am in a 10 page wizard and figure loading it all the time might not be as good just keeping it readily available, especially since I cannot load all fields without doing the ridiculous task of having to inspect the schema to get all field names etc...

Anyhow,  I'm going to guess this isn't a one shot answer.  So I'm expecting some more questions and discussion.

jason

<apex:inputFile id="irs_2009" value="{!uploadBody}" filename="{!rfq.irs_2009__c}" styleClass="input-file"/>
<apex:commandButton value="Upload Attachment" action="{!irs2009Upload}"  styleClass="upload-button"/>

public Blob uploadBody {get; set;}   
public PageReference irs2009Upload() { uploadFile('IRS 990 2009 - '+rfq.irs_2009__c); return null;}

public void uploadFile(String uploadName) {
    if(uploadBody != null && uploadName != null) {  
      Attachment att = new Attachment();  
      att.Body = uploadBody;
      att.Name = uploadName;
      save(); // this ensures that 'rfq' in the next line is not null
      att.ParentId = rfq.Id;  
      insert att;    	
    }   
  }