moderation issues

Is there any module which provide the functionality of paid members login only into drupal system? i.e. in "create new account" page I want a option where user can select the membership type and pay for that membership through online payment gateway. Only those users should have access of login into drupal, who have pay for membership. I have used CiviCRM but I didn't find any feasible solution for this.

I will really appreciate any help on this.

Thanks in advance.

On the drupal shop talk call today the issue of spam user registration came up (see notes). Laura suggested asking the question here.

How are people dealing with spam (in all its forms)
1) spam user registrations
2) spam content
3) comment spam

are you using Captcha or other user challenges?
Heavy moderation?
user based spam flagging?

let's here it!