DarWINE will eventually do this on intel Macs. At least for some applications. Crossover plugin will be the commercial implementation of that. (Already works for linux. See result reviews for that to evaluate whether it'll be worth the wait...)
My guess and hope is that Apple and Microsoft are working quite closely to bring a good version of Windows compatibility to intel Macs with a future version of VPC. It's been said that Apple's working with Microsoft on VPC.