ftp://ftp.infradead.org/pub/Sony-PS3/mars/MARS-OLS-2008.pdf It's sounds like a replacement for libspe2 (even though it's built on top of it). The SPUlets manage their own scheduling and workload (PPU programs can participate too). The author claims better performance than libspe2 if number of "threads" > number of SPUs. He also has 2 real-world examples: OpenSSL and zlib.
MARS 1.1 available Found this in the open source Cell development mailing list: http://ozlabs.org/pipermail/cbe-oss-dev/2008-December/006107.html
Stumbled on this while I was googling information about the SpursEngine. The Mars reference was found in this document. Here is a recent PowerPoint presentation about Mars. http://ftp.uk.linux.org/pub/linux/Sony-PS3/mars/presentations/MARS-CELF-20090903.pdf Seems like it is progressing well, the latest 1.1.4 update was in July this year.