so far I have come across these screen shot tools
but none that I came across would do scrolling screen shots; currently I only needed scrolling screen shots of web pages and I just came across a great tool for that - a firefox add-on called Abduction, it is really easy to use.
For full page screen shots (including all scrollable regions) or for cropped sections of a page. Just right click on the page and select 'Save Page as Image', if you are over an 'element' it will auto select that as the cropped area, you can then adjust the crop and save, if you want the entire page the easiest seems to be right clicking where there are no elements below the mouse and then adjust the fully selected page as needed
The saved png can then be opened in Shutter for applying arrows, boxes, etc...