What does 俗话说的好 mean?
俗话说的好 vs 俗话说

俗话说: As the proverb express. 

俗话说的好 means what the proverb says is exactly right or exactly fitting the circumstance/setting in the following statement. 

From grammar point of view, the form should be 俗话说得好. The structure is verb + 得 + extent/result complement. 

Some pedants would argue 俗话说 的 好 is a wrong expression. It looks that it's a common mistake by misplace 得 with 的. Personally, I wouldn't care about it since it's been widely used after all.