[jQuery] How to create Function libraries in jQuery?

I have a load of utility functions that I use across many of my
plugins. I'm including the ones each one needs in the plugins own code
atm. I've spent a few days trying to figuire out how to create a
single plugin/class that I can use as follows:

myUtils.doThis($('selector'));

and

$('selector').myUtils.doThis();

I've tried using name spaces but then 'this' inside each function
refers to the class not the jQuery object. Any and all ideas welcome.

I NEED
-----------
single class/item that has shared options
public and private methods that can accept parameters but also be
chained with the usual jQuery syntax!