I haven't been to Oskar Schindler's factory myself but other sights I'd recomment in and around Krakow are
Rynek Glowny - you'll probably find yourself passing through, eating, drinking and wandering arond there anyway
Gallery of 19th Century Polish Art above the Sukiennice - wonderful paintings, some huge canvasses, different styles including impressionist and symbolist and also Jozef Chelmonski 's "Four in Hand" one of my favourite paintings
Wawel - The Royal Castle and the Cathedral - beautiful, and historical location - the collections in the Riyal Castle, especially the tapestries, are very interesting
St. Mary's Church - go just before midday so you see Wit Stwosz's wonderfully carved altar screen being opened
Kazimierz, the Jewish Quarter and the Jewish Museum in the Old Synagogue - a real sense of history
Auschwitz - words can't really express what this is like
Salt Mines - never been myself but I'm told it's very good
Have a fantastic time in Krakow, it's a wonderful city!