Keen is the largest Psychic service online and has the largest selection of Psychics anywhere. They have virtually no screening process for their Psychics however so while there are a lot of Psychics to choose from, the quality is hit or miss. They do show you how long a psychic has been with Keen, how many readings they've done as well as reviews and ratings from previous customers which does help finding a real psychic.
Keen is the largest Psychic service online. They’ve been in business since the mid-90’s and were pretty much the first Psychic service offered on the Internet (it was all done over the phone in the past)