Can i add a Slide show to my website in a block. Is it possible for my Theme I would like to add  slide show to my website. How can i do that. And i would like to add it as a block in all the pages. What is the easy way to do that.

Please suggest.
You could do this with the Fields slideshow module https://drupal.org/project/field_slideshow and optionally the Colorbox module. 

Create a content type with an image field. Configure it so that you can load infinite images. Set the formatter of the image field as "slideshow". Then create a block with views and display the block in your sidebar.

Here is a good screencast to set it up: http://vimeo.com/26411524