My family comes from Wielun, Poland and then fled at WWII's onset in 1939. 
Specifically, they had an estate named Bolkov/Bolkuv/Bolkoff (don't
know exact spelling, but I've heard it pronounced "Bolkoof"). Would
anyone have any information on exactly where Bolkov is, or do you know
any details about it?

Dear 13monkey,

I have do doubt that the place you are looking for is Bolkow, with the
"w" pronounced like "v". There are several places of that name in
Poland, but only one near the town Wielun.

Please follow this link to see the location of Bolkow on a MapQuest
map, marked with a red star in map's center:
http://www.mapquest.com/maps/map.adp?latlongtype=decimal&latitude=51.3167&longitude=18.6333&size=big

Villages were often named for estates, and vice versa. Of course I
can't decide whether in this case, your family's estate was named
after the village Bolkow, or if the village received its name from the
estate. But I am absolutely sure that it is the correct place.

Bolkow is located 192.9 kilometers west-south-west of the Polish capital Warsaw.


Hope this helps!
Regards,
Scriptor



Sources:

ShtetlSeeker: Town Search
http://www.jewishgen.org/ShtetlSeeker/loctown.htm

Ada Holtzman Home Page: A Few Words to Marek
http://www.zchor.org/plock/tomarek.htm

Search terms used:
wielun bolkow
://www.google.de/search?q=wielun+bolkow&hl=de&lr=&newwindow=1&c2coff=1&start=30&sa=N

Excellent and thorough.

Currently Bolków is part of the "Gmina" of Ostrówek:
http://www.ostrowek.asi.pl/pls/ostrowek/portal?pageid=1166&ids=2

within the district of Wielu? ("Powiat Wielu?ski"):
http://www.lodzkie.pl/lodzkie/wojewodztwo/mapa/wielunskig.html

"Gmina = smaller district including several villages"
http://www.rtrfoundation.org/admindist.html
http://www.serwistlumacza.com/texts/polska.html#admin