Firstly, the Alpha Quadrant episodes of Voyager:
Caretaker (I and II)
Eye of the Needle
Non Sequitur
Future's End (I and II)
Message in a Bottle
Hope and Fear
Relativity
Pathfinder
Life Line
Inside Man
Endgame (I and II)
(Since there are quite a few of these, I've put the best ones in bold.)
Secondly, the episodes from various series that have been inspired by Groundhog Day, i.e. with time loops.
My basic rule of thumb here is that the episode has to involve multiple loops, so the Angel episode I Will Remember You doesn't count. Also, I basically have to exclude Seven Days and Tru Calling, since the whole series is based on a similar premise.
The episodes I'm thinking of at the moment are:
Buffy the Vampire Slayer: Life Serial
Charmed: Deja Vu All Over Again
Lois & Clark: The New Adventures of Superman: 'Twas the Night Before Mxymas
Stargate SG-1: Window of Opportunity
Star Trek: The Next Generation: Cause and Effect
The X-Files: Monday
Xena: Warrior Princess: Been There, Done That
Feel free to comment if you can think of any more that I've missed. (Credit where it's due: this page, this page, and this page were helpful in putting this list together, even though I didn't agree with all of their suggestions.)
I'd also like to give an honourable mention to 12:01, a vastly underrated film. This takes a more serious look at the subject - the protagonist is verging on a nervous breakdown by the end of the film. Sadly it's not available on DVD yet, but it's well worth watching if you get the chance.
