How to make a widget

Hi,
I want to make a jobs widget for my website.
I want to give samll script file for others(like how google giving for analytics,adsence) to use this widget.
And Jobs should be update automatically.
Now I am working with Asp.net 3.5 ,c# 3.0,VS 2008 with SPI.



Till now I did't developed any widget.


Pls guide me from scratch how make good and useful widget.


Thanks in advance.

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