The most important Muslim festival is the 30 day dawn-to-dusk fast. It was during the month that the prophet Mohammed received his revelation from Allah. 

Id-ul-Fitr
This day celebrates the end of Ramadan.

Id-ul-Zuha
This 10-day festival commemorates Abraham's attempt to sacrifice his son. It is celebrated with prayers and feasts.

Muharam
This 10-day festival commemorates the martyrdom of Mohammed's grandson, Imam Hussain.

Milad-un-Nabi
The birth of Mohammed.