Aria2
From Attie's Wiki
aria2c is a neat download tool that splits a file into chunks, and allows multiple connections.
Install
apt-get install aria2
Run
aria2c -x16 -s16 -j16 ${URI}
FTP
aria2c -x16 -s16 -j16 'ftp://${USERNAME}:${PASSWORD}@${HOSTNAME}/${FILEPATH}'