Local software mirrors
Some local software mirrors are provided for various Linux distributions.
Using the BitFolk software mirror will allow you to perform software updates without eating in to your data transfer quota. It will also likely be faster.
These mirrors will only be available from BitFolk IP space.
Mirrors for various versions of CentOS (x64_64 only) are available at http://mirror.bitfolk.com/centos/.
A Portage mirror is available for rsync mirroring from rsync://mirror.bitfolk.com::gentoo-portage.
See the Gentoo article for how to configure this.