~ Users generate transactions, which generates miners fees.
~ Users create services that accepts bitcoins as a payment option.
~ Users use services {Merchants} that accepts Bitcoin.
~ Users spread the word about Bitcoin. {Bitcoin Meetups & posting on forums}
~ Users create demand for bitcoins and this increase the value {price}
Let's list some more contributions that Bitcoin users bring to the table for this experiment to work. Once we have seen the value they bring, we will know how to make a success of this.
Aside from that though users don't do a whole lot to help the blockchain itself, they do external services like the ones you mentioned but that's all part of getting an economic system to run properly.