In one of the forums I subscribe to, the basic question was asked: "Which paid subscription sites do you suggest people use?"
I suggest caution. A friend of mine spent $300 for a year's subscription to one service and received almost nothing in return. (This was not entirely the service's fault as my friend lost his username and password at one point.)
On the other hand, I currently subscribe to the British service GenesReunited http://www.genesreunited.co.uk/
which costs about $25 for a 6-month subscription. It is basically a gedcom matching service. I have had good success connecting to other people researching my Linnen, Waller, Goldring, and Kinney lines through this service.
This past week I received a notice from GenesReunited saying that someone wanted to contact me regarding Ada Ing. I clicked the link. A message popped up saying:
"William Smith was my Maternal Grandfather as you will see from my tree. He remarried [after the death of Marion Ing] and had a number of children including my mother ...
I have Marion Ing's Bible which records a number of events including the death of Thomas Ing and the emigration of Ada and her mother.
I would like to exchange further information, but current work commitments don't allow me the time to respond immediately I will always reply to any communication
Wow! I was stunned! Thomas Ing was my great grandfather! I was very familiar with the story of my grandfather and his brother selling their oxen to pay for the passage of Marion's mother Martha and sister Ada to Canada in 1907.
I had never been able to find anything on William Smith, of London, England, born about 1880. This was despite frequent "possible matches" in GenesReunited. Now I had William's info, his parents' info, his second wif'e's info and the names and birth years of his 14 children!
Of course, if you don't have British ancestry, a GenesReunited subscription would be a waste of money. If you do have British ancestors, it may be worth checking out. (I have no connection to this company beyond being a satisfied subscriber.)