Yep, I use neverssl.com, when I remember it. Though, mostly I use example.com, since that works without SSL as well. I guess now I'll need to remember to type http://example.com .

Based off my experience, more and more captive portals appear to be letting the requests the OS makes to captive.apple.com or whatever through but still try to present a captive portal to the user. I can guess as to the motivation, but as a user it's danged annoying.