Extending ArcGIS
Creating a Python AddIn is probably the quickest and easiest approach if you just want to do some geoprocessing and deploy the tool to lots of users.
But as soon as you need a user interface (that does more than simply select GIS data sources) you should create a .Net AddIn (using either C# or VB.net).
I've created many AddIns over the years and they are a dramatic improvement to the old ArcGIS "plugins" that involved lots of complicated COM registration. AddIns are easy to build and deploy. Easy for users to install and uninstall.
.Net has excellent, powerful features for creating rich user interfaces with the kind of drag and drop that you require. And there are great books, forums, samples to leverage.
I've been tasked with a thesis project where i have to extend the features of ArcGis. I've been asked to create a model written in Python that can run out of ArcGIS 10. This model will have a simple user interface where the user can drag/drop a variety of shapefiles and enter the values for particular variables in order for the model to run effectively. Once the model has finished running, a new shapefile is created that lays out the most cost effective Collector Cable route for a wind turbine from point A to point B.
I'd like to know if such a functionality/ extension already exists in ArcGIS so i don't have to re-invent the wheel. If not then what is the best programming language to learn to extend ArcGIS for this (Python vs Visual basic vs Java). My background is Java, PHP, Jquery and Javascript. Also any pointers in the right direction i.e documentation, resources etc would be hugely appreciated