I would like to find the name of a story, and the text of the story
itself, that includes the following plot points. I believe it's an
Arthurian story from medieval England. I want to say Sir Gawain is
involved, but I can't be sure. Here is what little I remember about
the plot: a traveling knight is invited to stay witha rich man in his
castle or home in the country. The man tells him that he will not
accept any gift from the knight unless the knight lets him repay that
gift. The joke (or the twist) is that the man has an attractive wife
(or daughter?) who is interested in the knight. When the knight kisses
the woman, the man finds out about it and implies that the knight
should have to return the "gift" -- upon the man. The homoeroticism is
not so explicit, as I remember it. But it has been more than 15 years
. . . Do you know the story or the name of the story?

Hello gotisbrown3000-ga,

I believe the story that you're referring to is "Sir Gawain and the
Green Knight", a 14th-century English romance.

In the story, Gawain, a knight of King Arthur in Camelot, becomes a
guest at Hautdesert Castle.

From Wikipedia: http://en.wikipedia.org/wiki/Sir_Gawain_and_the_Green_Knight

"The lord's bargain
That night, the lord announces that while he spends the next day
hunting, the travel-weary Gawain shall stay at the castle, sleep as
late as he wants (even through Mass), and eat whenever he chooses to
arise; the lady will keep him company. But to add a little interest to
the day, the lord proposes a bargain: he will give Gawain whatever he
catches, on condition that Gawain gives to the lord, without
explanation, whatever he might gain during the day. Gawain accepts.
The next morning, after the lord has gone, the lady of the castle
visits Gawain's room and tries to seduce him, claiming that she knows
of the reputation of Arthur's knights as great lovers. Gawain,
however, keeps to his promise to remain chaste until his mission to
the Green Chapel is complete, and yields nothing but a single kiss.
When the lord returns with the deer he has killed, he hands it
straight to Sir Gawain, as agreed, and Gawain responds by returning
the lady's kiss to the lord. According to the lord's bargain, Gawain
refuses to explain where he won the kiss.
On the second morning, Gawain again receives a visit from the lady,
and again politely refuses her advances. That evening, when the lord
returns, there is a similar exchange of a hunted boar for two kisses.
On the third morning, when the lady visits his chamber, Gawain
maintains his chastity but accepts a green silk girdle, which is
supposed to keep him from harm, as a parting gift. But, the lady
insists, he must not tell her husband. That evening, the lord returns
with a fox, which he exchanges with Gawain for three kisses. However,
Gawain keeps the girdle from the lord so that he can use it in his
forthcoming encounter with the Green Knight."

You can find the original Middle English text from here:
http://www.hti.umich.edu/cgi/t/text/text-idx?c=cme;idno=Gawain

If you'd like a modernized text, you can look at here:
*http://livinghistory.co.uk/homepages/sirgawain/modtext.html

If you'd prefer a translation in modern English, you can also look at
these locations:
*http://www.lib.rochester.edu/camelot/sggk.htm
*http://rpo.library.utoronto.ca/poem/62.html

I trust this is what you're looking for.  If you need clarification,
please request for it using the "Request for clarfication" feature
before rating this answer.

secret901-ga

Search strategy:
I guessed it was Sir Gawain and looked it up on Wikipedia.