As far as I can tell, yamasa.org is the only site with animated writing. I was able to make it work the first time I tried it. I opened the dictionary and clicked on a kanji and it wrote it for me.

Play around with it. Maybe you’ll figure it out that way.

I don’t know of any websites that teach stroke order like that, but if you have an iPhone or iPod touch, try the app iKanji Touch. It’s very helpful and does stroke order in animation form.

I’m sure I’ve stumbled upon another good kanji animation out there (that actually drew the strokes—ones that just flash them up in order are easy to find) but I can’t remember where it was.

Here is a direct link to the Yamasa kanji dictionary: http://www.yamasa.cc/members/ocjs/kanjidic.nsf/SearchKanji3?OpenForm

You have to put actual kanji into the text box, you can’t use hiragana or romaji to search for the word first. If you are having difficulty typing it, just use any other dictionary and then copy and paste the character you want.

Sorry – I know you mentioned Web sites, but I don’t know of any web based practice software. What I do have (and use for my own kanji reminder drills) are games on the Nintendo DS intended for Japanese kids and adults. (Yes, even Japanese adults have to practice some of the lesser used kanji from time to time.)
Do you have a Nintendo DS? I can give you a short list of wonderful games (intended for Japanese kids) that coach you in correctly writing the kanji with the correct stroke order. If you have a DS and/or interest importing the games…

Maybe this site will be helpful to learn kanji stroke order.
Here’s demo version, which has 100 kanji.
http://www.infomongolia.com/lesson-category/67