How is the feet-washing ritual observed during Lent? How is the feet-washing ritual observed during Lent? How many denominations actually do this, besides the Roman Catholic Church and the Church of England? What is significance of maintaining this tradition to the modern era, and can anyone get its feet washed or wash the feet of others?
According to en.wikipedia.org , Foot washing is observed by many denominations, not only Roman Catholics. But in non-catholic denominations, the rite is not necessarily observed during Lent only. 

Excerpt from Wikipedia:


  Protestant practice:
  
  Foot washing is observed by numerous Protestant and proto-Protestant
  groups, including Seventh-day Adventist, Pentecostal, and Pietistic
  groups, some Anabaptists, and several types of Baptists. Foot washing
  rites are also practiced by many Anglican, Lutheran and Methodist
  churches, whereby foot washing is most often experienced in connection
  with Maundy Thursday services and, sometimes, at ordination services
  where the Bishop may wash the feet of those who are to be ordained.
  Though history shows that foot washing has at times been practiced in
  connection with baptism, and at times as a separate occasion, by far
  its most common practice has been in connection with the Lord's supper
  service. The Moravian Church practiced Foot Washing until 1818. There
  has been some revival of the practice as other liturgical churches
  have also rediscovered the practice.
  
  The observance of washing the saints' feet is quite varied, but a
  typical service follows the partaking of unleavened bread and wine.
  Deacons (in many cases) place pans of water in front of pews that have
  been arranged for the service. The men and women participate in
  separate groups, men washing men's feet and women washing women's
  feet. Each member of the congregation takes a turn washing the feet of
  another member. Each foot is placed one at a time into the basin of
  water, is washed by cupping the hand and pouring water over the foot,
  and is dried with a long towel girded around the waist of the member
  performing the washing. Most of these services appear to be quite
  moving to the participants.


In some churches, the Bishop may wash the feet of those newly ordained deacons.

Examples:


Unification Church USA.  Source
The Church of England: Source  (Notes 14)


  14 Foot-washing
  
  Before the Welcome, the bishop may wash the feet of the newly ordained
  deacons. Appropriate hymns or chants such as Ubi Caritas may be sung.
  After the foot-washing, John 13.12-17 may be read.