Hi!
I just got my Arduino Uno and I've thought of a project where I'll be using my Arduio and an ethernet shield to download torrents as a standalone hardware.
Can anyone tell me if this is even possible? 
Thanks alot guys.
I think you'll struggle to code up an implementation of the BitTorrent protocol within the memory constraints of an Arduino.
Download torrents to where exactly?
Download torrents to say SD Cards?
Ok... so now, you have two problems to fit in the 32k of program memory. You need to be able to implement a file system and the BitTorrent protocol.
Do you know much about it?
Have you tried turning on and off an LED and polling a switch?
arduino can do this. u can find SD library and Ethernet library from arduino.cc. you just need to good about torrent protocol. by the way it's a nice idea ...
Its very clear that some people have very little grasp of just how puny the processing in an Arduino is. Just using it as a very simple one page static html server is pushing it. You can get information in and out of the Arduino faster by serial than via ethernet. The PC you're reading this on probably has a million times as much RAM (literally). Think similar computing power to what put man on the moon in 1969.
In other words, no, not a snowballs chance in hell.
The Arduino is fabulous for what it was designed for, unfortunately most of what you use your computer for (assuming its less than 25 years old) doesn't fall within its capabilities.
In other words, no, not a snowballs chance in hell.
I would be impressed if this were implemented on my apple II, its got 126,000 bytes more memory and a hard disk interface
Just owning an Apple II at this stage of the game is impressive. 
I wish I'd kept some of my old computers.
It can do a weather widget with the aid of a second computer running Linux. 
(I thought I needed to get out more......)
Bit-torrent is appropriate for the computers of the day in 2001. 8 bit processors with memory bytes you can count need not apply.
yea its amazing what a 8 bitter can display when a 2.4 ghz celeron with 512 megs of ram is actually doing all the work and simply sending a serial bit stream to the slave
(I thought I needed to get out more......)
yea well you just wait till I finally break out the 86 Mac SE, I have a whole 16 bits and 4 Megs to play with there!
honestly the lowest machine I have ran torrents though is my 4 Meg DEC PC386SL/25 running debian, and its nails in eyes slow