WIC is available on WS2008, and Windows 7+. It requires full trust, but may be able to provide 50-100% speed improvements on simple resizing operations. (although not advanced ones). For better performance, libjpeg, ImageScience, etc may be a better route. (since both require Full Trust).

http://weblogs.asp.net/bleroy/archive/2010/05/03/the-fastest-way-to-resize-images-from-asp-net-and-it-s-more-supported-ish.aspx