Here’s a cool innovation for Moodle 1.9: Group specific blocks.
The idea is simple: one block that helps to communicate something different to each of your course groups. Handy for quick notes, directions or “secret communique”.
Download the block here: http://moodle.org/mod/data/view.php?d=13&rid=5414
Configuration is easy once the block is installed:
Set your groups,
Add the block
Configure the block.