First, these sweet, tiny crocheted hearts from Kristen TenDyke; these puffy little hearts made me smile.  Pattern Here.

Julie Kundhi has these flat crocheted hearts, which would make excellent gift embellishment, or glue a pin back on for a quick brooch.

And for a non-knitting, non-crochet, but all yarn-love option, try these wrapped yarn hearts from Woolywotnots.  Wouldn’t they be great on a small scale glued to cardstock for a sweet crafty valentine?