The best and most simple way is to get a blu ray player with a usb input. BE SURE that it supports MANY types of video codecs such as divx, xvid, mkv, MPEG4, AVI, WMV, etc. etc. Then all you have to do is dump the video on a flash drive and stick it in the player.
The raspberry pi makes an okay media center... I dunno though, I'd go the player route. Amazon will have something for you that would be inexpensive..... I'd do that over the pi.