Answer:
There are many online dating and internet dating sites springing up. Multiple dating sites provide various online services. Such as : matchmaking, instant messaging, live chats, dating forums and so on...
It really depends on what you're looking for, how old you are and what kind of experience you wish to have.
For marriage/old people - match.com and eharmony.com are the most popular
For free service - plentyoffish has a lot of members
For social online dating/networking try sowink.com, they're a newer site but I've heard many good things.