I emailed Mint.com asking about a Windows Phone and Windows 8 app and this is what I received today. I'm pretty excited about this response.
Greetings from Mint.com!
We are pleased to inform you that Mint will be available for both Windows 8 and Windows Phone 8 later this year, just in time for the holidays!
Thanks for taking the time to email us. Please let me know if you need further assistance.