1: New Year Parade (info here); 6: Twelfth Night Celebration (info here);
February
Chinese New Year Parade (info here)
March/April
Easter Parade (info here, date varies); St Patrick's Day (weekend around the 17th, info here)
May
Covent Garden May Fayre and Puppet Festival (date varies, info here)
June
to come (info here)
July
22: Green Fayre (info here); 29: Mela (info here)
August
Bank Holiday Weekend, end of the month: Notting Hill Carnival (info here)
September
Mid month: Thames Festival (info here); 23: Car Free Festival (info here)
October
to come (info here)
November
Guy Fawkes Fireworks (weekend around the 4th, info here); Lord Mayor's Show (date varies, info here)
December
Carols Under the Tree (info here)