The most common examples.

Wired Magazine's review of Rheingold's book notes the best known examples.
The book notes that both the Seattle World Trade Organization protests of 1999 and the demonstrations that led to the removal of Philippine President Joseph Estrada last year were aided by mobile phones and text messaging.
There must be more (Japan gets mentioned often) but wherever the successes of these smart mobs are noted, these two seem to be first on the list. Local political organizations, of course, make their own claims. (I may even have an historic one of my own.) From an independent media group in Ireland, for instance, we learn that:
Flashmobs and Smartmobs Are The Mobs Left Out Of The Dublin Riot Story
The indy-journalist writing the piece tells us that this particular demonstration (in late February, 2006) was the "first truly spontaneous 'smartmob' protest in Irish history". His praise seems more for the demonstration itself than for whatever it may have accomplished, but I admit that Irish English is often difficult for me to decipher, so perhaps I'm missing something.

It would seem that smart mobs are, by definition, physical entities. They're not virtual protest. But this form of protest also has its adherents (and apparently its researchers as well). The Electronic Civil Disobedience site announces numerous Virtual Sit-Ins (for instance, one that took place in July of 2005 to protest anti-immigrant websites) and gives reports on those that have concluded. The Digital Freedom Network's Activist's Workshop posts an article from 2003, Can Internet technology still revolutionize activism?. The Network would like to answer with a wholehearted "yes", though the overall impression of the article is quite a bit more hesitant about its effectiveness.

Go to: From the horse's mouth, or
Go to: Are crowds really that smart?