There are definitely many types of activism! I totally agree! Besides mass demonstrations, other types of work that I have done include:

• CopWatch -- going on patrol to monitor the police, as a means of preventing brutality
  
• Food & clothing redistributions
  
• Political prisoner support
  
• Books-to-prisons programs
  
• Running an infoshop and a free store
  
• Strikes and picket lines
  
• Organising boycotts

There is more, but I think that this gives some idea. I'm absolutely on the same page as you that street marches are not the only form of activism. However, I still think that chatting with friends, running a "fun & games" workshop, and dancing at the disco doesn't count as any of them...