Think handwritten greeting cards are remnants of a bygone era? Think again. Harvard-born 3-D greeting card startup LovePop Cards has landed $2.6 million in equity funding out of a planned $3.4 million goal, according to a Nov. 25 regulatory filing with the Securities and Exchange Commission. The investment marks the company's first significant funding round, after its intricate special occasion cards started gaining traction last year. The filing lists 20 undisclosed investors. A request for…