Anderson Cooper isn't in the closet. Neither is Richard Simmons (anymore). This list blows. Except for Kevin Spacey and Queen Latifah.
Here's my list:
Colin Farrell (But I think he's bi, not all the way gay, ditto Clooney)
I'm sure I can think of more, those are just off the top of my head.
Oh, and last but not least: The Big "O" (and Gayle)