"My will-be-one on Friday baby girl has developed a temper and a very unpleasant way of expressing it. She bites, hits, head butts, etc. when I take her away from something she wants to get into or sometimes if she's just mad. I want to nip this in the bud, no pun intended, but am not sure how to do it in the most gentle and affirming way. I want her to know it's okay to be mad but not okay to hit and bite. Is she too young for timeouts? Any other ideas? Redirect doesn't seem to work yet; she's incredibly strong willed."
Damned if I know.
Seriously, though, this is one of the toughest ages because you really can't do much of anything. They're not being aggressive to hurt someone else. They're just being aggressive because they're frustrated because they can't express themselves and because they have no control over their lives and environments. I can tell you what we did with El Chico when he was that age, but it didn't completely eliminate the problem for us, either. I think it's extremely important to remember that this is normal behavior for this age, so even if you can't get rid of it, you're not raising a monster and it'll get better (and then worse again, and then better, and then worse again, and then eventually they go off to college).
First, I made a concerted effort to talk to him about what was going to happen that day. In the morning I'd tell him what we were going to do for the whole day. Then right before we'd do it I'd tell him again, and as we were in transit somewhere I'd tell him where we were going and how we got there. He seemed to be calmer and in a much better mood when he knew what was going to happen that day, or where we were going when we were on the road.
Also, I was very sure to give him a 3-minute warning before removing him from any activity. Think about how pissed you'd be if you were reading a blog and all of a sudden your partner came and turned off the computer without telling you first. You'd throw your toys, too. Once I started giving the little warning ("We have to eat lunch now--say goodbye to your truck. You can play with it after lunch." Then give a couple of minutes for the kid to say goodbye.) transitions became so much easier.
Third, consider teaching some sign language. El Chico only picked up a few signs (milk, more, "all done" were the ones he used all the time) but they helped cut down on his frustration immensely. He knew I understood what he was trying to tell me, and we seemed to be able to understand each other better even when he wasn't using signs. (He had a friend who had over 30 signs by 12 months, and this kid was sooooo mellow. I think it was because she could basically say whatever she wanted to at that age.)
Four, keep repeating yourself. Remove her hands (or teeth) from you, repeat "no biting/hitting," and redirect her to something else. Repeat this 30 times a day for several months. It won't work, but the alternative is just to do nothing, which won't work either.
Five, remember that a strong will is the sign of a healthy child. It's driving you nuts right now, but it'll be an important trait for her later in life.
I think time-outs are only ever effective to remove the kid from the immediate situation as a redirect. I don't think it's a good punishment or disciplinary tool other than to change the focus of the situation for a few minutes. (I know people are going to write in about how it works so well for their kids, and how can I say it doesn't work, etc. I just think it's another system kids learn to game instead of learning from.) So it doesn't even make sense to label it a "time-out" for a baby that young. Removing her from the situation will probably work as well as anything else will at this age, though.
When El Chico was around that age, I read Lawrence Cohen's Playful Parenting and it made me look at discipline in a different way than I'd been thinking of it before. It doesn't have many practical solutions for kids under the age of 3 (and is probably best for kids 5 and up), but it switched my mindset and made it easier for me to deal with this super-frustrating stage when they're really out of control so much of the time.
Good luck. This is such a strange time because the energy you use to parent shifts and it's almost a completely different task.