Three is an incredibly difficult age for many children, especially the second half of the year. I think that there is a lot of cognitive development that happens at three, and it can really affect behavior.
You've already gotten some really good suggestions, but I'll just add mine for what its worth.
First, definitely read the two books Rachel suggested. I found the "How to Talk" book especially helpful. You might also try "Playful Parenting" by L. Cohen, which can give you some strategies on interacting with your daughter to find out what she is really thinking. At this age, her actions still say more than her words, and you may be able to find out what's behind her misbehavior through play. If you don't have time to read any other book, then read "Your Three Year Old, Friend or Enemy" by Ames and Ilg. This is part of a series of books on child development. It explains what behavior is appropriate at this age, what you can expect your child to be able to accomplish, and what coping strategies you can use for getting through the tough times. This book saved my sanity!
I will second using a rewards system rather than punishment. Stickers, the marble jar, an extra book at bedtime, special time with Mommy, whatever works. Definitely save time-out for the really big offenses, like hitting, and completely ignore something small like sticking her tongue out.
When your daughter refuses to do something you ask, or just ignores your requests, try asking in a fun way. Sing your request, or whisper it, or call it a super secret mission. You can also make a game of things like picking up. Ask her to pick up all of the red toys, then the blue ones. Or have her race against the clock.
I just remembered one other book -- "Raising Your Spirited Child." I haven't read it, but I've heard it is excellent.
Good luck. Three is tough, but it can be fun, too. Try to focus on your daughter's special qualities that make her unique and wonderful, even when she is frustrating you. That might make things easier.