The September issues of women's magazines are historically the thickest and most anticipated of the year, filled with a particularly frenzied orgy of materialism. WWD has the scoop on the covergirls for those issues, which will hit newsstands in late August. Keira Knightley will grace the cover of Vogue for the second time in under two years — the fourth time in total — even though her last cover from June '07 (pictured) didn't sell well. Glamour has Penélope Cruz, W is featuring Kate Hudson, In Style will highlight Uma Thurman, Allure has Carrie Underwood, Teen Vogue has Vanessa Hudgens, Elle has Jessica Simpson, and finally, Cosmo will show Blake Lively. (The teen queen's presence in Cosmo confirms our suspicion that the magazine is not actually geared towards grown women). [WWD, sub. req.]