Inevitably, the story about Jacob and his complicated love life raises a number of questions regarding the Jewish attitude concerning concubines and polygamy. Do Jews still practice polygamy? Outside Sephardic circles, polygamy has been banned for well over a thousand years, since the time Rabbanu Gershom outlawed it for Ashkenazic Jews.
Historically, there is no evidence of actual concubinage in the Talmud, nor is there any evidence of it in practice during the Middle Ages. In the responsa of Asher b. Jehiel (no. 32:1), there is a reference to a concubine, but it seems to be merely the case of a man cohabiting with a woman without going through a marriage ceremony with her, and not to a formal concubine. Modern readers would refer to such a woman as a “mistress.”
In general terms, the Talmud distinguishes between a concubine and a wife in the following way: Wives have ketubah (marriage contract) and kiddushin (formal marriage ceremony i.e., hupah) while concubines have neither. 
Ibn Daud adds in his notes to Maimonides, that any woman who does not dedicate herself to one man, is considered to be a harlot. 
However, Rashi takes issue with this definition. According to him, even a concubine must have kiddushin, but what she lacks is a ketubah (which delineates the financial responsibilities a husband has for his wife). In fact, Jewish law insists that even a married woman must have a ketubah, lest she be considered a concubine. Rashi’s opinion draws support from the Jerusalem Talmud (J. Ketubot 5:2, 29d). Most Halachic authorities generally rule in accordance with Maimonides and the Babylonian Talmud.
Opinions differ with respect whether a concubine is permitted or forbidden. Some scholars say that neither biblical or rabbinical law prohibits it. All that matters is that the concubine go to the mikvah ( a ritual pool of water) so that the man is not guilty of having sex with a menstruating woman (EH 26:1). The majority of medieval authorities conclude that concubinage is immoral. Radbaz, for an example, wrote back in the early 17th century, “Nowadays a woman is not sexually permitted to any man except through the formal marriage ceremony of kiddushin, Huppah, sheva brachot (the seven marriage blessings) and ketubah.” (Resp, Vol, 4 #225)
Only one notable 17th century authority, Jacob Emden (responsum no. 15), expressed the opinion that it should be permitted. Emden’s citations of talmudic sources endorsing polygamy show that some of the most famous rabbis of the Talmud were footloose and fancy free when it came to the question of concubines. In all likelihood, Rabbi Emden probably would have felt quite comfortable living in the 60’s.
In the past, among the Haredi communities in the United States, there seems to be some websites that actually advertise concubines for their Haredi followers.
The New York Daily News writes in their December 29th, 1996:
“A shadowy Brooklyn organization is recruiting married Orthodox Jewish men to enter extramarital relations by promoting the ancient biblical concept of concubines. The organization, which calls itself Shalom Bayis (‘Domestic Peace’ in Hebrew–my, what a funny oxymoron!), operates a telephone hot-line through which men can meet women willing to serve as concubines kept mistresses.” 
I am not sure whether this organization is still in business, hopefully it is not. However, Craig’s List and pilegeshpersonals.com routinely list Haredi men who wish to follow Rabbi Jacob Emden’s liberal attitude … Despite all the Halachic restrictions regarding concubines, men will forever remain men. It’s a shame we have evolved so little over the last 10,000 years of recorded history.
 (Sanhedrin 21a, Maimonides MT, Hilchot Melachim 4:4, cf. Lechem Mishna and Radbaz, ad loc.).
 Ibn Daud’s Glosses to Hilchot Ishut 1:4.