I love doing VFX within AE, I use it in every video I've done almost haha
Some great sites I've come across are:
AEtutsplus
creative cow (their after effects section)
motionworks
And then just searching on YouTube and on Vimeo for "After Effects Tutorials"
(sorry I'm not currently able to link the websites because I've not posted enough, so you'll just have to google them)