Castle is used to share small files quickly.
Sharenload is just another file hosting provider. They offer online storage/remote backup capacity, sophisticated uploading and downloading tools, plus they give users the ability to stream files when possible from the download page.
With Sharenload you can host files, images, videos, audio plus flash all in the same place.
YouSendIt lets businesses, professionals and consumers move big files. If you know how to use email, you can easily use the YouSendIt service. YouSendIt currently has over 9 million unique monthly users across 220 countries, over 6,500 paid users, and over 1 million registered users. More than 400 million files have been transferred using the service and YouSendIt is transferring over 30,000 gigabytes daily.