apt-fast is a shell script to accelerate apt-get downloads using Axel, a command line download accelerator. Based on apt-fast, some other scripts have been created and I though they are worth mentioning:

Remember apt-fast? Allow me to remind you: apt-fast is a simple bash script that speeds up apt-get download speed (so you would run "sudo apt-fast install firefox" to install Firefox for example) by using Axel, a command line application which accelerates HTTP/FTP downloads by using multiple sources for one file.