www.rainymood.com works for me. But my opinions on weather are... weird.
Gameswise... it's pretty much impossible to be unhappy while playing something obscenely cute, like Yoshi's Story or Gurumin.
I could also prescribe The Longest Journey, as even though some of the puzzles are obtuse enough to cause stress from frustration, April's voice has the opposite effect.
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"I'm Commander Shepard, and you're standing in the biggest library in Citadel Space. Look me up."