Sometimes I have used a flash pop up, but usually a java pop up...though again that is a rare occasion I use any pop ups at all.
I do like the use of a new window to a lot of iffy sites, I'd rather keep the surfer while he looks then have him close the sign up window...hell most of those are worse then their tours
As long as I can keep the surfer in my grasp the better the odds I can get A SIGN UP FROM HIM, AS LONG AS I DO NOT UPSET HIM ALONG THE WAY. Again this is on the link FROM my site....I know many LL's do not allow even a sponsor pop up, even less a webmasters one.
The tour would be on the same domain as the freeesite but would use links counted as outgoing.
Another bonus of this is I can fully track my offsite clicks. I KNOW if a surfer clicks to the sponsors sign up page.