Konqueror has gotten quite good as of KDE 4.8.x...

However, I'm having some trouble with the ad blocker. For security reasons I would like to block all iframes by default, with only a small number of websites whitelisted; but it's not obvious how to do so. Neither the ad blocker nor the general options window seem to have any options pertaining to iframes.

I hope I'm just missing something, because iframes are a major source of drive-by attacks on legitimate websites these days. (See for instance the recent NBC incident.) And not all drive-by attacks involve Windows malware; e.g. I've seen ones that use pure XSS exploits to modify Facebook account contents, and there's probably nastier stuff out there.

Does one have any recourse when using Konqueror, or is iframe blocking not included?

From what I can tell, iframe blocking is not included in Konqueror unfortunately.