Jet It! is a download manager written in Java for MacOSX.
Basically, it does what it sounds like it does. It watches all of your downloads and allows you to pause and resume downloads just like any other download manager. I assume that it can be ported to other types of operating systems being that it’s written in Java, but the current version is in a dmg which is only for MacOSX. It provides your usual statistics against the downloads.