eParties is the first company "incubated" by the venture, meaning it was conceived, built, and funded by eCompanies.
David Haddad, a former executive at toy manufacturer Mattel, has been named chief executive of the company.
The idea behind eParties is to find an easier, more direct way to plan parties and events, according to Dayton. Although details of the site's business model were not available, Dayton said it will tap into a $50 billion industry for party planning.
"Planning a party is an incredibly frustrating process," Dayton said. "It's frustrating and ripe for emotional stress."
eParties is the latest in a string of eCompanies investments and ventures. Last month the company took a minority stake in e-commerce and content site eHobbies. The company earlier secured $130 million in financing from companies including Disney, EarthLink, Goldman Sachs, Sprint, and SunAmerica.
When asked whether the companies they invest in are required to use "e" at the beginning of their names, Dayton said, "It's happy coincidence."