It cannot be any bigger than 1G.
You are subjected to advertisements (Buy my shoes, see this car, blah blah-- relitively tame).
You may want to have a higher-speed connection than just dialup.
It can be slow on the weekends (due to too many people using it, I suspect).
The website is http://www.yousendit.com
You don't have to register to send things, but you can, and it's free. As I said, you can send files up to 1G in size (and if you need to send files larger than that, I strongly suspect that there may be something either wrong with you, or you are a profesional in some field and do not know any better).
For whatever it is worth, there you go.