Not just as series, but basically all individual games in the series:
Bruins-Hawks, especially the final game
Kings-Blues, especially the first couple games
Of the rest, one that sticks in my mind is game two of Detroit-Anaheim, where the Ducks stormed back from 4-1 in the third to send it to overtime. Oh, and Leafs-Bruins game 7. Lots of great comebacks this year.
Montreal - Ottawa Game 3 (6-1 win, line brawl, local rookie hatty)
Toronto - Boston Game 7 (Boston down 4-1 with 10mins to go, comeback)
Pittsburgh - Ottawa Game 3 (Alfie ties it with a SHG with 30 secs, Greening wins it in 2OT)
Pittsburgh - Boston Game 4 (the favourite for the East gets swept)
Chicago - Boston Game 4 (very high scoring and entertaining)
As a series, I really enjoyed Chicago - Detroit and San Jose - LA.