Most of Duke's NCAAT games are in the NCAA vault website (
NCAA Vault) starting with '86 NC game against UL till the '11 AZ butt kicking. Some years they only show final four games, some only to the elite 8, and some show games from the round of 16 (it's really cool to watch JWill in the '01 UCLA game).
For ACC games there is also an ACC vault (
ACC Vault). I especially like the Duke vs. UNC additions they have put on there in the last couple years.
Youtube is also a great place to watch old games, and if you like Duke vs. Michigan in the fab 5 era, check out their first game in '91 (
Part 1) (
Part 2). The quality isn't great (obviously originally recorded on VHS) but its still a great game.