In Argentina I often hear the word (or prefix?) 're' meaning 'very/real/really'
Some examples are:
La prueba fue re difícil
La película era re chota
Estoy re bien
It's a prefix. This is what RAE says:
re-. (Del lat. re-).
pref. Significa 'repetición'. Reconstruir.
pref. Significa 'movimiento hacia atrás'. Refluir.
pref. Denota 'intensificación'. Recargar.
pref. Indica 'oposición' o 'resistencia'. Rechazar. Repugnar. Significa 'negación' o 'inversión del significado simple'. Reprobar. Con adjetivos o adverbios, puede reforzarse el valor de intensificación añadiendo a re- las sílabas -te o -quete. Retebueno. Requetebién.
In the uses you provide, it's the third meaning, where it's used to intensify the adjective.
I think in Spain "requete-" is more used than "re-", at least in some cases. In fact, if I hear someone say rebueno I automatically think they're from America.
requete- is used as a more emphatic version of re-. In the popular reasoning, it makes sense that it is bigger since it includes the word. :P
Are there any rules regarding the use of 're'?
First, as said in other answer, it's a prefix, not a word.
It should be used only colloquially, in casual speak. It's emphatic and slightly childish. In general, you'll prefer 'muy'.
This is very common in Mexico as well it is considered very improper but it is used very often in social situations to reenforce and remark a word. The most common is
El examen fue redifícil
to say it was not just hard, but really rehard.
Is 're' an abbreviation of another word? (Maybe realmente?)
Sometimes it's used as recontra, especially if used as stand alone word. Not sure of the etymology, my first thought would be bidding in contract bridge where one of translation of double and redouble is contra and recontra. But that just my impression, could be totally wrong.
A derivative of re- is requete- sometimes used to indicate something even more intense, than re-.
Is 're' used anywhere else apart from Argentina?
Yes, it's very typical in Mexico,it is used in other Latin-American countries (eg. in Peru).
The expression "re" is very common in my country (Colombia) and it has the same meaning you implied, basically to augment the effect of something.
Its usage is more common among young people. Older people do not use it as much, or sound kind of off when they they say it.
I do not think it is an abbreviation of another word. I believe it works as an adverb.
I can attest it is pretty common in Colombia in all generations up to the gen-x, and, from previous interactions with other people, I know for a fact it is widely used in Venezuela too. It most likely is often used in Chile and Mexico as well.
The only rule I can think of regarding its usage is that it almost always precedes an adjective. I.e. He is very TALL --> He is re TALL; that said, it can also precede verbs, but that usage is less common. i.e "La re cagué" (I screwed up BIG TIME), highly informal usage, mainly among friends.
By the way, it is highly informal. Do not use it in formal conversation. In that case replace "re" with "muy", "bastante" or "demasiado".
Soy de argentina y sí, se usa solo acá. Como dijieron anteriormente, se utiliza para intensificar algo (verbos y adjetivos, sobre todo) Y no, no hay reglas concretas de gramatica porque no creo que se una palabra "oficial"
Te lo comiste a Juan? Sí, me lo re comí.
Messi es re buen jugador.
¡Anoche la cena estuvo re linda!
Ese pibe esta re bueno
Aquella montaña rusa es re divertida
Etc
Espero que te haya servido!
I am not a native speaker but...
Some other answers seem to be confusing re- as a prefix and re as a word, a slang equivalent of 'muy' (= very). As an example in context (from Gaturro, referring to a smartphone)
¡¡Está genial, re cool, re moderno!!
Estoy seguro de que esta partícula re (p.ej., "recontar") se oye sólo en la Argentina. Hasta ahora no se puede encontrar de dónde lo sacaron los Argentinos. Re significa "muy" y el también sufijo "-ísimo", igualmente tiene el significado de "gran", "grande", "súper"... En vez de decir : Buenísimo, decimos : Rebueno.
A veces, si queremos ir más allá de la intensificación, el esquema resultará así: Rebuenísimo o Recontrabuenísimo.
Cabe notar que "recontra" se usa frente a una palabra que empieza con la consonante R.
No se dice "rerápido" pero sí "recontrarápido".
Lo empleamos con un verbo casi del mismo modo que si fuera un adjetivo o sustantivo, sólo en ese caso él tomará el significado intensificado del verbo.
ej:
estoy refeliz esta noche.
tengo una relija ( un gran Hambre)
este bondi viaja recontra rápido
esta frutilla, me la recomí anoche. ==== en este caso, significa que : anoche yo me comí la frutilla con muchas ganas, y me la disfruté mucho.
reviajar = viajar mucho y con muchas ganas...
re=muy=very