[wp-hackers] Allow authors to create new users but only as Contributors

[Dino Termini]

Hi,

for a project that I'm working on, I need to give Authors the capability 
to create new users. Using the Members plugin, this was just a matter of 
a few clicks.

The tricky part is now to restrict this functionality so that Authors 
can only create Contributors or Subscribers, but not Authors and above.

Also, if a given Author has capability my_custom_enable_something, the 
new user s/he creates should inherit that capability as well.

Can someone point me into the right direction or explain how to 
implement such a thing?

Thank you,
Dino.