You can already download IE8 Beta 2, now featuring InPrivate Browsing. Excerpt from the site:
Sometimes you don’t want to leave any trace of specific web browsing activity, such as when checking e-mail at an Internet café or shopping for a gift on a family PC. InPrivate Browsing in Internet Explorer 8 helps prevent your browsing history, temporary Internet files, form data, cookies, and usernames and passwords from being retained by the browser, leaving no evidence of your browsing or search history.
Pretty awesome, huh?