We have added several packages to Scientific Linux 5.4 that were not in the Scientific Linux 5.3 release.

fuse - Provided by vendor
Summary: fuse is now provided by The Upstream Vendor. So it is no longer "added" but merely part of the release.
fuse-smb and fuse-sshfs are still added by Scientific Linux

imlib
Summary: Imlib is a display depth independent image loading and rendering library.
This is not installed by default.

iwlwifi-5150-ucode
iwlwifi-1000-ucode
Summary: Firmware (ucode) for Intel wireless
These are installed by default.

lua
Summary: Lua is a powerful light-weight programming language designed for extending applications. Lua is also frequently used as a general-purpose, stand-alone language.
This is not installed by default.

madwifi - Equivalent provided by vendor
Summary: Support for the Atheros chipset in now in the kernel and release. Because of this support from the Upstream Vendor, we have taken madwifi out of SL 5.4

rt61pci-firmware
rt73usb-firmware
Summary: Firmware (ucode) for Ralink wireless
These are installed by default.

XFS - Driver provided by vendor for x86_64
Summary: The xfs kernel module is now compiled in the x86_64 kernel, but not the i686 version. Because of this, the 32 bit (i386) distribution is using kernel module rpm's, while the 64 bit (x86_64) distribution is using the xfs kernel module actually in the kernel.