I have a squareish face and really dark brown hair thats kinda shoulder length. I might dye it, maybe black, with red or pink and blonde streaks?

here are some good tips for haircuts to match your face shape...just scroll down to "square":
http://backtoschool.about.com/od/style/a/flattering.htm

here are some ideas that I think are nice for a square face:
http://img222.imageshack.us/img222/8587/brittanykramerlargemsg1al1.jpg
http://www.squirlmunk.com/images/walls/ShannynSossamon.jpg
http://a426.ac-images.myspacecdn.com/01447/52/40/1447340425_l.jpg
http://www.quasimodobell.com/MusicData/9999%20S/SIMPSON%60%20ASHLEE/__FIXED_ashlee%20simpson%20-%20001.jpg

Some of them might be too long for your current length...I think the last one is the best. I think you should dye it black with cool red streaks; but not big streaks all the way down but like the way avril lavigne did in this pic:
http://i.ivillage.com/BS/wouldyou/BS_AvrilLavi_Ryan_325.jpg