When Benjamin Sun was a boy in Queens, he switched from a homo-geneous Catholic institution to a public school. The difference between the two student bodies shocked him. Pablo, Leroy and Sayed became his new friends.    More than a decade later, Mr. Sun is making diversity his business. He runs a successful group of ethnic-oriented Web sites aimed at Asian-Americans, African-Americans and Hispanics. Despite a collapse in the new media market, 4-year-old Community Connect is impressing investors, luring advertisers and winning applause from its audience.    The firm raised $20 million in venture capital in the past two years and counts Hewlett-Packard and General Motors among its sponsors. Its three sites, AsianAvenue.com, BlackPlanet.com and MiGente.com, combined boast more than 3 million registered members and in excess of 491 million page views a month.    The former Merrill Lynch investment banker says he's driven by a sense of personal accomplishment. Members of his three online communities-

where people meet, exchange ideas and play games-regularly send e-mails to site managers informing them of spouses they found, career changes they made or illness cures they found through the sites.    Mr. Sun inherits his entrepreneurial spirit from his parents, both Taiwanese immi-grants. After studying in New York City, they got married-during his mother's lunch hour-and later opened up a restaurant and a printing business. Mr. Sun says his father wanted him to keep his stable job as a banker. But he thought the risks were worth it.    "I'm not only redefining the industry, i'm also changing the way a real-world commu-nity lives," Mr. Sun says.   -ALEXIA VARGAS