Robert Ferguson discusses this in his The Vikings: A History, and most of this answer is pulled from that work.

The Norse attitude towards homosexuality was certainly negative. Delivering an insult that implied that the recipient was homosexual was a grave act; "shame-poles" would use the bodies of mares to identify the target as feminine, thus suggesting that the target behaved as a woman sexually.

Therein lies the difference between the blanket Christian denunciation of homosexuality and the Norse approach—to the Norse, homosexuality was much more shameful if you "received" sex in the same sense of a woman. Being accused of being either party, penetrative or receptive, in the homosexual act was an insult. However, insults implying that you were the receptive partner, and thus the feminine one in the Norse mind, were much more serious, and someone insulted this way, according to the Grágás, could respond by legally killing the insult-er. Interestingly, homosexuality itself wasn't directly illegal, but merely incredibly shameful. In an honor-bound society, however, the difference between the two is almost irrelevant.

I am unaware about the status of lesbian relationships in Norse society, but perhaps a specialist might know more. I suspect that they go relatively unconsidered, because the feminizing shame of male homosexuality obviously has little effect on homosexual women.