Parallelizing Multi-Protocol Utility for Downloading Files
http://sourceforge.net/projects/aria2

aria2 is a utility for downloading files. It has completely new design
concept from its predecessor, Aria, and is written from scratch. aria2 has
a segmented downloading engine in its core. It can download one file from
multiple URLs or multiple connections from one URL. This results in very
high speed downloading, much faster than ordinary browsers. This engine in
was implemented in a single-thread model. The architecture is clean and easy
to extend.

aria2 currently supports HTTP, FTP, and BitTorrent.