ConnectFusion

ConnectFusion is a download manager that can accelerate your downloads by launching multiple threads to the remote server.

It supports the resume feature and is capable of restarting a broken download due to lost connection. ConnectFusion includes an easy-to-use interface and its installation does not interfere with the normal behavior of your browser.
ConnectFusion is free, never expires, and does not contain any spyware or advertisement.
ConnectFusion source is available to any one who wants to download, inspect or modify it.