This code is easy but very very useful for specific design purposes. Its great to be able to change bloggers default distance between your sidebar gadgets. Some designs will look better with a greater distance, some with a very small gap.
Template → Customise → Advanced → Add CSS
Then paste the following code:
The above code places "6" lines between your widgets, either increase the number 6 for a greater distance or decrease the number for less space/lines.
That's all folks, any questions though, just comment.