The primary means for distributing SIL Linux software is through a package repository that targets recent releases of Debian and Ubuntu. This will parallel the main distro repository, and provide SIL-only packages or newer versions of SIL packages that are also in the upstream distro repository. This package repository can be accessed at http://packages.sil.org/
Currently we are discussing the design and setup of the SIL Linux repository system in Repository.
For non-repository based systems, such as Mac and OLPC, there is a software download area here.