Ancestry.com's Immigration and Naturalization Collection is free through September 6, 2010. Here's the link: http://www.ancestry.com/immigration
Included in the collection are passenger lists, immigration and naturalization records, border crossings and passports, and a new entry in the collection, New York City, Ellis Island Oral Histories, 1892-1976.
There is also a free immigration webinar tonight, September 1, at 8pm EDT. This is short notice; but check back, because Ancestry.com's webinars are typically archived for viewing later. Advance registration is required here.