Huffington Post notes that:
If unions move to support the protests in a major way, that could mean thousands more people marching in Lower Manhattan. Thus far the protesters have not managed to come near the 10,000 or so who attended the unrelated May 12 march on Wall Street.
Occupy Wall Street protesters have also been reaching out:
"There's a lot of good feeling. They've made a lot of friends," said Chuck Zlatkin of the postal union.
When a band of about 100 protesters showed up at a postal workers' rally featuring Rep. Jerrold Nadler (D-N.Y.) on Tuesday, complete with purple hair and big drums, "they went a long way towards touching people and making connections," Zlatkin observed.
WNYC reports that, in addition to the unions Chris named yesterday as planning to join a Wednesday afternoon Occupy Wall Street rally—the Transport Workers Union, SEIU locals, Workers United and the United Federation of Teachers—the Communications Workers of America will also be joining.
With all this, there appears to be real movement, from both directions, toward a coalition or at least cooperation between Occupy Wall Street and unions.