For freebie software, check out http://www.versiontracker.com or http://www.macupdate.com. They have search options so you can find programs that are built for making greeting cards, however nobody can guarantee those programs will work (properly). They take submissions by everyone from major corporations to teenagers who're punching out their first programming efforts. Its worth a shot to check'em out though. Beyond that, however, you can create greeting cards in various word processors, including apple's Pages. I love the program myself, but some folks havent found it to be the most intuitive. Additionally, while it has starter templates, its more of a raw 'start from scratch' program.