Make a sign up sheet, then allow all users that signed up to be emailed

I would like to create a sign up page, where users would sign up for an event, then allow administrators to contact all members who have signed up. Which modules would I use for this?

I would also like to be able to contact all members of a specific role, and specific OG, but most modules for that are not yet 6.x compatible.

Finally, I would like to make it so when a user selects a certain option from a dropdown list in the registration form, they are automatically added to the corresponding group (ex. if there was a drop down list of eye color, if a member chooses "brown" they are added to an organic group called "brown eyed users").

Thanks, all help is much appreciated!