Now that I've finished my scripts (two episodes of a TV show), I am trying to revise them and then animate them with a friend.

My concern is that I have little knowledge of acting and I fear my friend is in the same position. Thus I would like to gain some basic understanding of acting, to allow us to better create the facial expressions, vocal tones and who knows what else that is required to do the script justice, and also to help me write better in future.

So does anybody know of any online resources for people interested in learning to act?

So you're making an animation? That's cool (if you are).
I don't think there are too many online acting things. But, one of the things I did a lot when I was working on my animations was that I watched a lot of cartoons and even more movies/shows, studying the expressions for use for the actual animation.
I'm not that great at acting, but, as I've always understood it, the most important thing to keep in mind while acting is to put yourself in the shoes of the character. Read books or scripts that you can find and record yourself to see what you like.
It may not be totally professional, but it's not really that hard (well, acting as a career is, but what you're doing doesn't have to be).

Sorry I don't have anything better to say, but I hope that helps a bit.

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I tried to be perfect, it just wasn't worth it.
I don't know how it got so bad.
It's hard to believe me, it never gets easy.
I guess I knew it all along.

The good, the bad, and the H.A.C.K

I probably won't be much help, either. I can only say that I can write only because I learned how to act, but maybe that's just me. I took acting classes back in the 1990s, and the most important parts of what I learned (especially that all-important question, "What's my character's objective?") stuck with me and still guides my writing (and my acting too, if I ever get back into it).

Of course, you could always Google...

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Script Frenzy 2008: Spanner -- WINNER!
Project Blog: Spanner's World