a lot of people would disagree with me but i would recommend learning from books, rather than lifting examples from script archives.
that way, you learn the language really well and actually understand what you're doing very well. you can also claim the copyright for your scripts etc.
if you want to do "clever-looking menus" then it's far, far safer (and easier) to use flash. i say safer, because something like 98.7% of web users have the flash plug in. with javascript, there are lots of different versions and old crappy browsers will screw up your code and it'll all go tits up. sometimes.
I would recommend the following books (and i get 15% comission )
Teach Yourself JavaScript in 24 Hours
Teach Yourself Flash MX in 24 Hours
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