Sedo
Sedo allows you to list your domain for sale and is the largest aftermarket domain name sales house in the world.
As far as parking goes, Sedo can monetize international traffic better than most, as it has offices in Germany, England and the USA (and advertisers from these and opther countries, as well).
Sedo monetizes poker domains well, though the payout for each click is smaller.
Sedo also displays listings that are more appropriate.
Sedo uses Google as its parking partner, so it is probably showing Google Adwords listings?
NameDrive
NameDrive does well with many names that aren't getting international traffic.
You do not have to list your Domain for sale at NameDrive, even if it is. This is good because it creates click confidence and more visitors will use the site (click on the PPC Ads).
NameDrive seems to monetize adult, poker, blackjack and gambling names well.
NameDrive seems to have a decent or better click through rate than some other PPC programs.
NameDrive allows lots of categories, a keyword and has many custom headers to chose from.
GoldKey
GoldKey offers great configurability, not only allowing for lots of header banner graphics and custom theme color choices, but for domain/title customization ("Apache Webmasters.com" instead of "apachewebmasters.com" - which allows you to stand-out your keywords), adding a slogon, offering a reciprocal links directory, note taking and the ability to over-ride keywords with choices of your own.
GoldKey is owned by Yahoo and shows Overture PPC Listings.
GoldKey stats are supposed to be updated in real time, but are not.
GoldKey sometimes has a problem with new domains, check the listings after parking them and making sure they look good. Go back once in a while, too. You may have to move some names to other systems, GoldKey seems to have problems with some names no matter what.
GoldKey claims to pay the most on clicks, but doesn't. It's great at monetizing the traffic, though.
Fabulous
Fabulous is considered to be the king of all parking programs. I have just started there, but Fabulous is now monetizing Domains that had never had a click before. The Fabulous 5.0 parking program has been released which allows some category and keyword/related customization for non-adult and non-poker/gambling domains.
Fabulous pays out the best for poker/blackjack/roulette/gambling names anywhere in the industry and knows how to monetize such domains.
Fabulous is looking secifically for Type-In domains and generic search keyword phrases and does not like traffic from link farms, forums, etc.
You need to have at least 100 strong Type-In or keyword search domains accepted into the program inorder to join-up.
Fabulous also offers a great $6.75 wholesale domains registrations to its parking partners. This is for dot com, dot net and dot org, only, though. And it is only for the member, not for the member to resell registrations.
Fabulous has EXCELLENT domain name keyword optimization.
There really is no better program than Fabulous'. It not only offers premium parking, but roar and dark blue parking programs, as well. Domains that do not fit in the premium parking program may do OK in one of these programs, but require more attention and optimization. But usually if a name is not in Fabulous' premium parking, the name may do better somewhere else.
DomainHop
DomainHop is actually quite spammy. It has pop-ups like *****. There is probably a secret way of getting rid of these pop-ups, but it doesn't work for anyone I know.
DomainHop can monetize some names well, though. I keep a couple parked there. DomainHop is owned by Kanoodle and has high ad percentage revenue share rates.
Domain Hop will even pay for domains with no clicks, but high traffic. You can earn 4 cents a day if you have at least 4 visitors a day on a domain, even when no one clicks on anything. This allows high traffic names that get no clicks a way to pay for themelves.
NOTE:
*NEVER* click on any of the PPC listings shown on any of your own Domains. This can get you cicked-out of the program. Visit the pages and check-out the categories to make sure they are appropriate, but leave the PPC ads alone.
LINKS:
Sedo NameDrive GoldKey Fabulous DomainHop
There are others as well. Domain Sponsor is supposed to have great optimization and be great for banking/insurance/stocks type names. TrafficZ is popular. Dotzup is new. SmartName is interesting.

Hope that helps!
