One of these groups is "Tryzub" (Trident), which was originally formed as a paramilitary unit of the Congress of Ukrainian Nationalists but then became an independent organisation.
The second group is the "Maidan Action 'Right-Wing Sector'" (Акція на Майдані "ПРАВИЙ СЕКТОР"), a movement formed on the social networking web-site VK.
Also seen by the President Administration is Dmytro Korchyn'sky, leader of the "Bratstvo" (Brotherhood) party. Korchyns'ky is widely considered an agent provocateur, and his "Bratstvo" already took part in several actions that were meant to provoke police suppression of peaceful protests. Moreover, it is said that Korchyns'ky taught a course at the explicitly pro-Putin "Seliger" summer camp in Russia.
UPDATE 1: It seems that individual members of Svoboda and C14 took part in the attacks on the President Administration, but it seems that Svoboda's leadership did not sanction the attacks. Furthermore, Svoboda's leader Oleh Tyahnybok was one of the leaders of the opposition who tried to persuade the crowd by the President Administration to stop their actions and join the peaceful protests on Maidan.
UPDATE 2: The newly discovered video footage suggests that not only right-wing extremists were provoking the police. They might have been joined by dozens of hooligans (titushkis) who were paid by the authorities.