Arm cross-compilation works with pretty much any arm toolchain. There are not too many specific instructions necessary.
Todo : list of confirmed cross-compiled packages.
The usual eros guides:
Toolchain Bridge : convert an existing toolchain into an ros-ready toolchain.
Cross Compiling : using eros as a cross-compiling environment.
The following are a list of guides written pre-eros that may be more or less useful to those developing on arm.
gumros - original guide for users putting ros on a gumstick.
gumstix-ubuntu-qemu : rough guide on using qemu to do a gumstix install (Cedric.Pradalier).
nao - gumros style instructions for the nao robots (Daniel Maier).