If you want to upload a bitmap copy of a movieclip, you can do that as Lillemanden said,
but if you want to upload a swf file, as Anthony Kanago said, it depends on the hosting service.
A really weird and long work around would be to a bitmap copy of a movieclip on a hosting service and a xml or sql entry on your server which will hold the details of the animation, if any( tweens, porperties, symbols, etc. ) and have that linked to the url of the uploaded image so you could offer a 'click here to view animation' link. When the user clicks the jpeg, you will redirect to a swf that will playback the right swf according to the image originally clicked.
A more 'realistic' answer would be encoding the swf animation as a gif using actionscript.
There is a handy library here:
http://www.bytearray.org/?p=93
I tried it and it's pretty easy to use.