1. The Stylish City: http://thestylishcity.com/nyc-sample-sales-this-week
You can sign up for their newsletter to stay in touch of sample sales and other great information. They list these events every week. They list sample sales by categories, which is great since you can see which ones sell clothes, shoes, jewelry, and accessories.
Racked has an amazing list of sample sale events listed by day, which allows you to see when each sample sale is happening.
3. Some designers and retailers having sample sales: Cynthia Rowley, J.Crew, Ippolita, and Shoshanna.
Tess Giberson Sample Sale
Cynthia Rowley Sample Sale Flyer
Hope this small list helps! Let me know in your comments below.