Where can I find reviews of, and recommendations for, portable air
conditioners -- the new free-standing models that vent through windows
rather than sitting in them? I can't find anything about them at the
Consumer Reports website and the only reviews I've been able to find
on Amazon.com related to the DeLonghi brand (while I'm interested in
all the other brands as well).

Try these sites:
http://adwordscentral.air-conditioners-america.com/?source=adwords-portable-air-conditioner-review
http://www.allergybuyersclub.com/compare-air-conditioners.html
http://www.epinions.com/Air_Conditioners--reviews--stand_alone_portable
http://www.airpure.com/portable-air-conditioner-reviews.html
http://www.nextag.com/portable-air-conditioners/search-html
http://www.allergybuyersclubshopping.com/ac-ra-9km.html
http://adwordscentral.air-conditioners-america.com/ed_AC_comparisons.asp

Here's a buyer's guide:
http://www.portableac101.com/?gg=us&kw=portable%20air%20conditioner

Hope this helps!  If you need anything further, just let me know.