Auto resize big images

Is there a way to shrink images to ‘regular internet’ size?

I mean if users upload pictures straight from the camera, this is very possible, sizes upto 4000x3000px, can these be resized automatically to say 1024×860 or something similar?

I have WP users I can want to explain they should fix this on their pc before they start uploading. (if they would listen anyway, they say this works on all modern website comparing this to flickr, facebook, etc)

Or is there a plugin? Or a way to fix it? Can someone point me in the right direction? Would be awesome ??

Cheers,
Vincent