By Shaykh Abu Bakr Jabir al-Jaza'iry
Zakat-ul-Fitr is a Sunnah that is obligatory upon every individual Muslim. This is due to Ibn Umars statement, may Allah be pleased with him:
The Messenger of Allah made Zakat-ul-Fitr obligatory during Ramadhan as one Sa of dried dates or one Sa of barley upon the slave and the free man, the male and the female, and the young and the old of the Muslims. (Al-Bukhari and Muslim)
From the wisdom of Zakat-ul-Fitr is that it purifies the fasting soul from the effects of useless, non-beneficial speech (or acts) and obscene speech (or behavior). Likewise, it keeps the poor and needy people from having to beg on the day of Eid.
Ibn Abbas, may Allah be pleased with him, said: The Messenger of Allah made Zakat-ul-Fitr obligatory as a purification for the fasting person from useless, non-beneficial speech (or acts) and obscene speech (or behavior), and as a means of feeding the poor. (Abu Dawud and Ibn Majah, and it was graded Sahih by Al-Hakim). 
The Prophet saws also said:
Keep them (the poor) from having to beg on this day. (Al-Bayhaqi - and its chain of narration is weak)
The Amount and Type of Food
The amount of Zakat-ul-Fitr is a Sa' and a Sa is four Amdad (cupped handfuls). It is given from the usual staple foods of the people of the land, whether it is wheat, or barley, or dried dates, or rice, or raisins or cheese. This is due to the statement of Abu Said (may Allah be pleased with him):
When the Messenger of Allah was among us, we used to give Zakat-ul-Fitr on behalf of every person, young and old, free or owned (i.e. a slave), as a Sa of Taam, or a Sa of cheese (dried milk) or a Sa of barley or a Sa of dried dates, or a Sa of raisins. (Al-Bukhari and Muslim)
It is Only given from items of Food
It is obligatory that Zakat-ul-Fitr be given from the types of food. Money should not be given in place of it, except if there is a pressing need to do so. This is because it is not confirmed that the Prophet gave money for it in place of food. It has not even been reported from the Companions that they gave money (for Zakat-ul-Fitr).
Zakat-ul-Fitr becomes obligatory with the coming of the night
of the Eid (i.e. the night before the 1st of Shawwal).
It is to be paid a day or two before the day of the 'Eid, as
Ibn Umar used to do, and the time of giving generosity,
which is from the time Fajr comes in on the day of the Eid
until just before the prayer (Salat-ul-Eid). This is due
to the Prophets saws command that Zakat-ul-Fitr be given
before the people come out to the prayer. Ibn Abbas, may
Allah be pleased with him, said:
The time of making it up (i.e. paying it late) is after the Eid prayer and anytime thereafter. Zakat-ul-Fitr may be given during this time (following the prayer) and it is acceptable, however it is disliked (to give it late).
The recipients of Zakat-ul-Fitr are the same as the recipients of the general Zakat, except that the poor and the needy have more right to it than the other people who have a share in it. This is based upon the Prophets statement:
Keep them from having to beg on this day. (Al-Bayhaqi and its chain of narration is weak)
Therefore, it is not given to other than the poor, unless there are no poor people or their poverty is light (i.e. not severe) or the need of others besides them, who have a share in it, has become severe.