According to whois-Search.com...
Here is a list of registrars and which "Drop" services they are in kahoots with:
VeriSign.com ( networksolutions ) - Snapnames
domaindiscount24 - rrpproxy.net - R51-LROR - Snapnames
BulkRegister.com - Snapnames
4domains.com - Snapnames
1dni.com - Snapnames
namebay.com - Snapnames
pairNIC.com - Snapnames
Nominate.net ( BB Online UK Limited ) - Snapnames
TotalNIC.net - Snapnames
NameSecure.com - Snapnames
DomainName.com - Snapnames
Catalog.com - Snapnames
domainmonkeys.com - Snapnames
planetdomain.com - Snapnames
dotster.com - Namewinner
namesdirect.com - Namewinner
newdentity.com - Namewinner
namezero.com - Namewinner
namefull.com - Namewinner
fm-net.ne.jp - Namewinner
stargateinc.com - Namewinner
shop4domain.com - Namewinner
personalnames.com - Namewinner
edge.jp - livedoor.com - NameWinner
rgnames.com - NameWinner
idregister.com - NameWinner
webnic.cc - Namewinner
Communigal.net - Sitename.com - Galcomm.com - Namewinner
fabulous.com - Dropwizard
addresscreation.com - Buydomains
enameco.com / e-names.org - Buydomains
omnis.com - Buydomains
registrationtek.com - Buydomains
1accredited.com - Buydomains
123registration.com - Buydomains
domainzoo.com - Buydomains
domaindiscover.com - Buydomains
dynadot.com - Buydomains
secura-gmbh.de - Buydomains
melbourneit.com - Ultimate Search
namebargain.com - Ultimate Search/Buydomains
directnic.com - NOLDC.com / keywordtraffic.info
safenames.net - TheFirstname
iaregistry.com - Dropking
bookmyname.com - NameFox
ascio.com - NameFox
itsyourdomain.com - NameFox
bestregistrar.com - NameFox
libris.com - Euro box
dotforce.com - drop club
paycenter.com.cn - drop club
alldomains.com - drop club
srsplus.com - drop club
eastcom.com - drop club
yesnic.com - drop club
doregi.com - drop club
bizcn.com - drop club
godaddy.com - Godaddy
wildwestdomains.com - Godaddy
bluerazor.com - Godaddy
enom.com - Enom club drop
centralregistrar.com (domainmonger) - Enom club drop
namejuice.com - Enom club drop
Namescout.com - Pool
NameSystem.com - Pool
signaturedomains.com - Pool
moniker.com - Pool
psi.jp - Pool
domainthenet.com - Pool
encirca.biz - Pool
Rebel.com - Pool
NamesBeyond.com - Pool
srspartner.com - Pool
directi.com - Pool
ausregistry.net - Pool
registersite.com - Pool
domainregistry.com - Pool
nameking.com - Pool
signdomains.com - Pool
000domains.com - Pool
Domainstobeseen.com - Pool
ar.com - Pool
Domainca.com - Pool
DomainSite.com - Pool
Parava.net - Pool
esoftwiz.com - Pool
domainbank.net - Pool
TotalRegistrations.com - Pool
awregistry.net - Pool
vividdomains.com - Pool
biditwinit.com - Pool
usawebhost.com - Pool
fiducia.lv - Pool
neonic.com - Pool
dotearth.com - Pool
dodora.net - Pool
esite.com - Pool
nameview.com - Pool
domainpro.com - Pool
domainpeople.com - Pool
name.com - Pool
mynamenow.com - Pool
transecute.com - Pool
vedacore.com - Pool
nameintel.com - Pool ?
1stdomain.net - Name Administration Inc
domainit.com - Name Administration Inc
007names.com - Name Administration Inc
annulet.com - Name Administration Inc ?
psi-usa.info - domaincatcher.com
R68-LROR - domaincatcher.com
dotregistrar.com - dotregistrar domwish
Looks like pool has a ton of registry connections
