John the Baptist has long had admirers, supporters, and devotees.
225. The cult of St. John the Baptist has been present in the Christian Church since ancient time. From a very early date, it acquired popular forms and connotations. In addition to the celebration of his death (29 August), of all the Saints he is the only one whose birth is also celebrated (24 June) – as with Christ and the Blessed Virgin Mary.
Why would the birthday of John be important? It might be that remark of the Lord’s about no person born of a woman (to that point in history) being greater than he.
In virtue of having baptised Jesus in the Jordan, many baptisteries are dedicated to him and his image as “baptizer” is to found close to many baptismal fonts. He is the patron Saint of those condemned to death or who have been imprisoned for the witness to the faith, in virtue of the harsh prison which he endured and of the death which he encountered.
Baptistry dedications, yes. I remember a stained glass of him where an immersion font was eventually installed in my very first parish assignment. The deacon wanted to install the water pump outside the window so it would appear as if water were pouring from the River Jordan in the depiction.
An interesting bit of religious astronomy:
In all probability, the date of John the Baptists’ birth (24 June) was fixed in relation to that of Christ (25 December): according to what was said by the Angel Gabriel, when Mary conceived Our Savior, Elizabeth had already been with child for six months (cf Lk 1, 26.36). The date of 24 June is also linked to the solar cycle of the Northern hemisphere. The feast is celebrated as the Sun, turning towards the South of the zodiac, begins to decline: a phenomenon that was taken to symbolize John the Baptist who said in relation to Jesus: “illum oportet crescere, me autem minui” (John 3, 30).
Do you know of any community that still lights midsummer bonfires?
John’s mission of witnessing to the light (cf John 1, 7) lies at the origin of the custom of blessing bonfires on St John’s Eve – or at least gave a Christian significance to the practice. The Church blesses such fires, praying God that the faithful may overcome the darkness of the world and reach the “indefectible light” of God (Cf. Rituale Romanum Pauli V Pontificis Maximi iussu editum….Pii XII auctoritate ordinatum et auctum. Tit. IX, cap. III, 13: Benedictio rogi in Vigilia Navitatis S. Ioannis Baptistae).
The Directory on Popular Piety and the Liturgy is online at the Vatican site.
Catholic Sensibility 
I think bonfires survive (or have been revived for tourism) in the northern regions of Europe, and Quebec. Not very common in the US except as an ethnic curiosity, it seems (well, outside of Alaska, the US doesn’t experience much profound winter darkness). See: http://en.wikipedia.org/wiki/Midsummer