For example, in Hungarian Revolution of 1848 participated Polish Legions with their general, Józef Bem. After revolution he became national hero in Hungary.
The Polish also helped during the Hungarian Revolution in 1956. This time was very difficult to Poland because of PRL (Polska Republika Ludowa - Polish People's Republic) and being controlled by Soviets. Despite this, people from Poland helped as they could - e.g. by sending blood (there were about 11,000 blood donors) or medicaments (44 tons (!) were sended by planes and even more by trains). Because of this, all the support from Poland was bigger than from the USA.
Not only did Poland helped Hungary, but also they helped us. When the Polish-Soviet war started, no one wanted to help us. It is important to know that it was only two years after restored independence by Poland, so the country was very weak.
That time Hungary sended us a lot of ammunition and wanted to send us soldiers, but other countries didn't agree.
Polish version:
Polak, Węgier — dwa bratanki,
i do szabli, i do szklanki,
oba zuchy, oba żwawi,
niech im Pan Bóg błogosławi.
Hungary version:
Lengyel, magyar – két jó barát
Együtt harcol s issza borát
Vitéz s bátor mindkettője
Áldás szálljon mindkettőre.
It can be translated as:
Pole and Hungarian cousins be,
good for fight and good for party.
Both are valiant, both are lively,
Upon them may God's blessings be.
I really wanted to go there once again! :)
(later I'll place here some photos from Hungary - now I can't find them^^')