I'd say pretty much all the tutorials here are worth seeing, they're fantasic for picking up odd things you didn't even know you ought to know, as well as teaching you loads of tips and tricks and new creative methods.
Regarding other sites vidocopilot.net has probably the most consistently brilliant collection out there, but other sites have some good stuff.
http://maltaannon.com and
http://allbetsareoff.com/ have some great videos and
http://aetuts.com/ is shaping up with quite a few nice things. (But search first - they've often already answered :D )
I know what you mean about collage - there's more then enough AE help on the web to learn pretty much everything, and anything you get stuck on the forums here will answer expertly.
Most important is to fiddle a lot. Pause tutorials and try to guess where they might be going, try and make a variation of the effect when you've finished. Mess around with different filters and see what you can make, most of all have fun with it. Nothing is so satisfying as the first time you work out how to do a complex effect all yourself.
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Only in after effects do children get to pick and whip their parents.
http://hennell-online.co.uk
