So here's a tricky little thing. Know all those spammers that have joined up recently? They still have profiles. Like RobinSwinton and injurylawyer17. And those profiles also list the sites they're hawking.
At the time I looked, RobinSwinton didn't even have any posts to her name, so there was no spam to alert someone. I just happened to join when they were on, and got suspicious.
It's a little harder to go through the new user lists, so guess who that job is going to fall to, I suppose... sorry, Clueless. It doesn't really clutter up the forums, just the site, though, so maybe it's lower priority. Go through and sweep them out once a week or something, maybe.
And because this seems like a time when it needs to be said, we really, really do appreciate the time and effort you put into keeping this site a going concern. Thank you.
I'm hoping to get some additional revisions in place between now and the end of the year to get Planewalker more active again as a real center of planar goodies. 
I learned that another effective way of cutting down spam, especially with sign-ups is to have a hidden field (one using the css properties display:none and name it something common like phone or faxnumber) that should never be filled with any values at all. On the server side if it has a value other than "" then it is invalid and never entered into the system. This works at least now since many spam bots tend to fill out all input fields they find and wouldn't check for css properties just what's in the html.