A toolchain is a complete collection of compiler and binutils programs and can be run either as a cross-compiler, or native on the target (if performance allows).
Not a complete distribution, just a Linux toolchain. But it's a toolchain built and maintained for MIPS with commercial support available, and free snapshots.
MIPS Technologies UK maintain their own source tree for the toolchain components. They resynchronize infrequently with mainstream GNU releases (which inevitably have bugs for minor architectures such as MIPS) and focus on providing the most reliable, best-performing compiler for the largest range of MIPS CPUs.
This is the same compiler which is at the heart of our MIPS SDE embedded toolkit. You can now get it in RPM format:
Native big-endian ftp://ftp.mips.com/pub/tools/software/sde-for-linux/sdelinux-5.01-1.mips.rpm; native little-endian ftp://ftp.mips.com/pub/tools/software/sde-for-linux/sdelinux-5.01-1.mipsel.rpm; Linux/386 cross for big-endian target ftp://ftp.mips.com/pub/tools/software/sde-for-linux/sdelinux-5.01-4eb.i386.rpm; and Linux/386 cross for little-endian target ftp://ftp.mips.com/pub/tools/software/sde-for-linux/sdelinux-5.01-4.i386.rpm.
MTUK would like to hear how well it worked, so contact them on mailto:sde@mips.com.
See the section on commercial distributions - these all include appropriate toolchain deliverables.
H.J. Lu distributes a toolchain as part of his Red Hat 7.1 port. It can be found at ftp://ftp.linux-mips.org/linux/mips/redhat/7.1/.
A stable set of toolchain components provided by Maciej can be downloaded from ftp://ftp.ds2.pg.gda.pl/pub/macro/ or the mirror. This is based on gcc 2.95.3 (patched) and up-to-date binutils.
Dan Kegel has a page at http://kegel.com/crosstool/ with a nice script to automatize the build procedure.