Well there is always the standard spam with sponsors, but I'm sure you already doing that.
First of all what most people overlook is the serious potential for them to be a good source of traffic, very high quality traffic i might add.
Secondly I suggest providing services in your email
ie. have you ever seen those lame ass simple quiz scripts that tell you what memebr of the simpsons you are? why not send them an html page kinda like that, but 'What kind of porn surfer are you?'.. quiz em.. and then when they submit have it post to a script and pump out something based on their input.. ie. 'You are a Teen porn surfer - You like em young and tight'.. and then something.. 'You REALLY should check out a couple of THESE site' These kind of gimmicks provide INSANE results.
This is just off the top of my head, I'm sure you can come up with plenty of good idea.. just try and be original and you'll do great.
Happy spamming
