crop photo at angle?

Is there a way to crop a photo at an angle, e.g. the crop rectangle would be at say a 25degree angle to the horizontal? This is more of an adjustment than can be made with the Straighten tool. If iPhoto cannot do this, what other apps can?

using iPhoto 09, Snow Leopard

PS, is anyone else dissatisfied with this new forum setup which doesn't have separate forums for different version of the software? And when I posted this question, the search turned up answers from other forums as well such as the Final Cut Pro forum, no use at all.