Setting vars in jQuery / JavaScript
Your code is great so far.
The only tip I can think of is to wrap grouped variables inside a namespace / singleton.
This would make it easier to debug and perform operations of group of related elements.

    // GENERAL VARS
var UpRate = 250,
    DownRate = UpRate,
    OpenHeight = "25px";

// SET IPP VARS
var $IPP = {};
$IPP.Wrapper = $("div.iqPaginItemsPerPageWrapper");
$IPP.Default = $IPP.Wrapper.children("div.iqPaginDefault");
$IPP.NonDefault = $IPP.Wrapper.children("div.iqPaginNonDefault");
$IPP.Options = $IPP.Wrapper.children("div.ItemsPerPage");
$IPP.Value = $("span#ItemsPerPageValue");

// SET SB VARS
var $SB = {};
$SB.Wrapper = $("div.iqPaginSortByWrapper");
$SB.Default = $SB.Wrapper.children("div.iqPaginDefault");
$SB.NonDefault = $SB.Wrapper.children("div.iqPaginNonDefault");
$SB.Options = $SB.Wrapper.children("div.SortBy");
$SB.Value = $("span#SortByValue");

// CREATE SB TEXT ARRAY
var SBTextArray = [];
SBTextArray[1] = "Company Name A - Z";
SBTextArray[2] = "Company Name Z - A";
SBTextArray[3] = "Product Name A - Z";
SBTextArray[4] = "Product Name Z - A";
SBTextArray[5] = "Model Number A - Z";
SBTextArray[6] = "Model Number Z - A";


1) Use a namespace for related elements and functionality.

2) It depends. In most cases it doesn't matter unless if you different tags with the same classes. Like p.class1 and dd.class1. More info here

3) You could just use an object literal to store the message by a reference name.
Something like this.

var listing = { az: {}, za: {} };
listing.az.company = "Company Name A - Z";
listing.az.product = "Product Name A - Z";
listing.az.model = "Model Number A - Z";
listing.za.company = "Company Name Z - A";
listing.za.product = "Product Name Z - A";
listing.za.model = "Model Number Z - A";


I think your current code is good enough though.