Although it seems like the pro-immigrant rallies in NYC (NY Times article here) weren't as large as in other major cities (AP article via MSN here, LA Times article here), the impact of the "Day without Immigrants" was certainly noticeable at my school. The halls were pretty quiet all day long, and a number of teachers told me that most of their Latino students didn't attend school. A bunch of my kids (all Latinos) came to school but skipped after school to attend rallies with their parents or older siblings. They all called it a "huelga," or strike, instead of a rally or boycott, and seemed pretty excited to take part in it. One undocumented kid stayed in after school and told me a few too many times that he wasn't scared of immigration officials at the rallies. Even with the massive show of force by immigrants around the country in recent rallies, the fact that this kid was still scared shows how pervasive the fear is in some immigrant communities.
Interestingly, as the NY Times article points out, there was a real division among the different immigrant populations. Almost all of the South and East Asian students came to school, and most of the Asian kids I talked to didn't seem very interested in what was going on. This is probably a function of the organizing power of the Latino media and the fact that there are more Latino immigrants than other groups. Still, it seems like these rallies creating more of a Latino movement (and from what I can tell there are even divisions between recent immigrants from Mexico, Ecuador, Peru, etc and immigrants from the Dominican Republic) and not necessarily a movement that extends to all immigrant populations.