How to build an app where I have virtual 3x5 cards the user can fill in and move around on screen

You might want to write your front end in flash.

I imagine the final version of this will be a combination of ColdFusion and alot of JavaScript.

I imagine you'll use CF to handle simple stuff like communicating with your database (getting/saving/etc.), and then utilize a bunch of JavaScript to manage the client-side interactions of drag-n-drop, sorting, positing, etc.

And to minimize annoying page refreshes, I suggest you'll want to use a lot of AJAX to help with continually tracking and saving card positions, content, etc.

I don't really know of anything out there that could provide a base for this specific of a project, but at the very least you'll definitely want to get yourself a good JavaScript library (jQuery, ExtJS, mooTools, etc.) that can help with the drag-n-drop and other client interaction stuff.

Also, you'll definitely want to carefully plot out how all the peices of this need to work together.  Otherwise, you'll end up with a pile of CF/JS/HTML/CSS spaghetti that will be impossible to manage, much less expand upon in the future.