Change display sidebar elements by user group type (guests, users, moderators etc)

I wonder, if i want to make each group to see other elemets, for example:

guests- will see "you can register here: click here"

users- will see "welcome to our site"

moderators- will see "good mornning"

It is just example.

I know it based on the boardSidebar template but im not sure what to write exactly.

If you have plugin for this ill glad.

Nice! Thanks!