44. James and Alexa Hirschfeld

Cofounders, Paperless Post

Brother and sister James and Alexa Hirschfeld launched e-commerce website Paperless Post in 2009. Paperless Post allows users to create and customize virtual and paper stationery.

In April, Paperless Post raised $25 million in a Series C round from Tim Draper, Ram Shriram, Mousse Partners, SV Angel, RRE Ventures, and August Capital. Its last round valued the company at about $150 million.