On the night of 4th December, 2009 the four baths - Széchenyi, Gellért, Rudas, Király - offer special music programs with DJs from 22.00 to 01.30.

There will be a free transfer between the four baths. Tickets are available in the baths at 2900 forints (11 Euros).

From 5th October, 2009 the visitors of some Budapest thermal baths are given 50% discount on entrance fee on weekdays:

Monday: Dagály Bath
Tuesday: Lukács Bath
Wednesday: Dandár Bath
Thursday: Gellért Bath
Friday: Csillaghegyi Bath

Source and more info:
Budapest Spas and Hot Springs