One of the special garments to be worn by the Kohanim as described in our Parsha was the Kesoness (כתונת), a coat or a tunic made of linen which was for the Kohein Gadol as well as for the ordinary Kohanim (שמות כ"ח: ד,ל"ט-מ'). In describing the Mitzvah to make this garment for Aharon's sons, who were the first ordinary Kohanim, the Torah states simply that Kutanos (כתנות), tunics, were to be fashioned for them (שם פסוק מ'). The Yerushalmi in Yoma (פרק ג' הלכה ו', דף ט"ז:) records a discussion concerning the Torah's use of the word Kutanos (כתנות), tunics, in the plural form, in this Posuk. One opinion holds that the plural form is used regarding each son of Aharon; Kutanos, tunics, in the plural, were thus made for every single Kohein. Each individual Kohein, then, received two Kutanos. According to this view, therefore, the word Kutanos is used by the Torah not as referring to the group collectively, but to each individual specifically. The other opinion, though, posits that the plural form is used because there are several Kohanim who will need this garment, and thus several Kutanos had to be made for them, as a group. Each individual Kohein, however, received only one. In discussing the Halachos of the Kesoness and the other Bigdei Kehunah, the Rambam (פרק ח' מהל' כלי המקדש) makes no mention of a requirement for a regular Kohein to have more than one, seemingly accepting the second opinion.
The Gemara in Megillah (דף ז.) presents an interpretation similar to the second opinion above regarding the Mitzvah to distribute Matanos LaEvyonim, gifts to poor people, on Purim. Since the Posuk in Megillas Esther (ט:כ"ב) from which this Mitzvah is derived states that Matanos (מתנות), gifts, in the plural form, must be given to Evyonim (אביונים), poor people, in the plural form, one might conclude that the Mitzvah is to give at least two gifts to at least two poor people. The Gemara therefore says, as explained by Rashi (שם בד"ה שתי מתנות), that although one must indeed give to at least two poor people, as the word Evyonim implies, only one gift must be given to each. The word Matanos, gifts, thus refers to what must be given to the group of (at least two) poor people collectively, but not to what must be given to each individual poor person specifically.
The Turei Evven (באבני שהם למגילה שם בד"ה מתנות) notes that this Gemara is clearly following the view of the second opinion in the above Yerushalmi, and that the first opinion there would indeed require one to give at least two gifts to each poor person to fulfill the Mitzvah of Matanos LaEvyonim. The Pri Chadash (אורח חיים סימן תרצ"ד ס"ק א') explains that we do not in fact require this on Purim, despite this opinion in the Yerushalmi, because of the grammatical construction of the phrase ומתנות לאביונים in the aforementioned Posuk in Megillas Esther. The Ran in Megillah (דף ג: בדפי הרי"ף בד"ה ומשלוח) writes that whereas the Mitzvah of Mishloach Manos is to give away at least two food items (to at least one person), the Mitzvah of Matanos LaEvyonim is to give only one gift (to at least two people) because for a poor person, even one gift is considered of great value.
The Rambam (פרק ב' מהל' מגילה הלכה ט"ז) rules in accordance with the above Gemara that one must give a gift, which may be an actual present, or money, or food, to at least two poor people. The Shulchan Aruch (או"ח שם סעיף א') writes this as well, although less explicitly; the Chayei Adam (כלל קנ"ה סעיף כ"ח) spells it out clearly. The Mishnah Berurah (שם ס"ק ב') raises a question from the Pri Megadim (שם במשבצות זהב ס"ק א') as to the minimum value of each gift to the poor, but then cites the Chidushei HaRitva in Megillah (דף ז. בד"ה תני) who says that one fulfills the Mitzvah by giving at least two Perutos (which equals a few cents), no less than one Perutah to each poor person, because anything worth a Perutah may be considered a gift. He then adds that the Pri Megadim himself (שם) believes that one must give each poor person something from which he can benefit on Purim itself, either food which he can eat on Purim, or money which he can spend on Purim.
The Shaarei Teshuvah (שם ס"ק א') quotes one opinion which holds that the Matanos given to each of the two Evyonim must equal in value the minimum worth of the two food items one must give for the Mitzvah of Mishloach Manos; since the minimum amount given (to at least one person) for Mishloach Manos is an amount which suffices for a (small) meal, one must give each poor person either food or money enough for such a meal. The Shaarei Teshuvah (שם) quotes the exact amount and says that if this is correct, one does not fulfill the Mitzvah by giving each poor person a Perutah's worth; he himself, though, does not appear to accept this opinion. The Kaf HaChaim (שם ס"ק ז'), however, quotes others who hold this way as well, and rules that one should be stringent and try to fulfill the Mitzvah according to all views by giving this larger amount; this must be done, though, for only the minimally required two poor people, and if one wants to give to others as well, he may give whatever he wants. The Rambam (הל' מגילה שם הלכה י"ז) notes that one should preferably spend more money on Matanos LaEvyonim than he does on his Seudah and on Mishloach Manos.
The Shaarei Teshuvah (שם) also quotes a view that if one gives the value of two gifts to one poor person, one fulfills his obligation, although it is improper to do so; he himself, however, rejects this view, saying that most Poskim rule that one must give to at least two poor people. The Kaf HaChaim (שם ס"ק י') quotes that a poor man and his wife (assuming she's also poor) can be counted as two separate people for this Mitzvah; if one has in mind when giving money to this couple that he wishes to fulfill his Mitzvah (and he gives the value of the minimum amount for each), it's considered as though he gave to each one separately, and he indeed fulfills the Mitzvah. The Aruch HaShulchan (שם סעיף ב'), however, believes that one does not fulfill his Mitzvah by giving to a couple or to different family members who live together, because they are viewed as one individual. The Bach (או"ח סימן תרצ"ה בד"ה וצריך) writes that if one has a lot of money to distribute, he should give a little bit to many poor people rather than all the money to one or two people, because by so doing, he is helping save many more lives and is thus entitled to a greater reward.
The Ramo (או"ח שם סעיף ד') rules that women are obligated to give Matanos LaEvyonim and Mishloach Manos just as men are; the Shaarei Teshuvah (שם ס"ק ט') quotes that this is because אף הן היו באותו הנס, women too benefitted from the miracle of Purim, and were among those who subsequently accepted all the laws of Purim. The Magen Avraham (שם ס"ק י"ד) says, though, that a married woman may rely on that which is given by her husband if he gives to more than the minimally required number of people, although he considers it proper for a woman to be stringent and give on her own. The Chayei Adam (כלל קנ"ה סעיף ל"ג) and the Mishnah Berurah (שם ס"ק כ"ה) concur. The Aruch HaShulchan (שם סימן תרצ"ד סעיף ב') says that a woman can indeed fulfill her obligation via the gifts given by her husband, because they are like one, but other members of the household who are obligated to give must give on their own. It is worth noting that the Matanos LaEvyonim must be distributed on Purim day, not at night, as the Magen Avraham (שם סימן תרצ"ה ס"ק י"ג) rules, and not before Purim as he quotes (שם סימן תרצ"ד ס"ק א') from earlier sources. The Kaf HaChaim (שם ס"ק ט"ו) notes that if the gifts are distributed on Purim day, even if the giver sent them from afar well before Purim, he fulfills the Mitzvah.