Citations:

British Medical Journal; BMJ; International edition; London Jun 15, 2002 324; 7351 p. 1407-1408
Written in response to recent events in Britian, specifically the legalization of second-parent adoptions by a second mother. It seems that studies on the effects of being raised in same-sex environments started in the seventies, and that at that time:

These young adults did not differ from their counterparts from heterosexual families in terms of quality of family relationships, psychological adjustment, or quality of peer relationships. With respect to their sexual orientation, the large majority of children from lesbian families identified as heterosexual in adulthood.

It was specifically noted that these early studies were primarily done on women and children where the child was born in a hetersexual marriage, and followed by divorce or separation. It would seem logical that children born to two women through assistive reproductive technologies such as artificial insemination would suffer fewer problems than the earlier children born in families that were eventually divorced.

American Sociological Review. Vol 66(2), Apr 2001, pp. 159-183
A rather interesting article in its coverage of how research in this field is performed. Research can be tainted a number of ways, and researchers on both sides claim the other is tainting the research through flawed design. This particular author is of the opinion that no credible research exists that supports the idea that same-sex parenting of children is in any way harmful to the child.

We wish to acknowlege that the political stakes of this body of research are so high that the ideological "family values" of scholars play a greater part than usual in how they design, conduct, and interpret their studies. Of course, we recognize that this is equally true for those who cricize such studies (including Wardle [1997], Lerner and Nagai [2000], and ourselves).

This particular author goes into detail relating to the various studies done, and critiques them. She also identifies the key researchers producing studies showing that such parenting is harmful.

Even though the American Psychological Association expelled Paul Cameron, and the American Sociological Association denounced him for wilfully misrepresenting research (Cantor 1994; Herek 1998, 200), his publications continue to be cited in amicus briefs, court decision, and policy hearings.

and

Wardle(1997), like other opponents of homosexual parenthood, also relies on a controversial literature that decries the putative risks of "fatherlessness" in general. Thus, Wardle cites books by Popenoe (1993, 1996), Blankenhorn (1995), and Whitehead (1993) when he argues[...]

Scandinavian Journal of Psychology. Vol 43(4), Sep 2002, pp. 335-351
I wasn't able to get the full article, only the abstract. However, the abstract did contain this line:

Children raised by lesbian mothers or gay fathers did not systematically differ from other children on any of the outcomes. The studies indicate that children raised by lesbian women do not experience adverse outcomes compared with other children. The same holds for children raised by gay men, but more studies should be done.