Having used Firebird, I highly recommend Netscape 7.2.
Wasn't expecting that, huh?
Anyway, I think netscape has a 'cleaner' feel to it. But then again, Firebird is smaller. It's all a matter of preference I suppose.
There's also Pow! by AnalogX... the only thing is, you have to tell it which pop-ups to block. However, since they're all nearly the same (popups and ads, that is), it's pretty easy to compile a list and not worry about it again.
If anything, head over to tucows or download.com and just type in pop-up blocker. I've found it's pretty useful to find the most inane/obtuse/useful of programs.