Linus announced Linux v2.6.17 yesterday, among the usual long list of improvements, fixes, and features is the following:
David S. Miller: [SPARC64]: Dump local cpu registers in sun4v_log_error() [TG3]: Handle Sun onboard tg3 chips more correctly. [SPARC64]: Avoid JBUS errors on some Niagara systems. [SPARC64]: Set appropriate max_cache_size. [SPARC64]: Do not double-export sys_close() when CONFIG_SOLARIS_EMUL_MODULE Krzysztof Helt: [SPARC]: Migration cost tune up in sparc smp.
If you want to fire up a ready-made distro on your Niagara, read what InfoWorld says about Ubuntu on the UltraSPARC T1 and download the Ubuntu 6.0.6 ISOs from your favorite mirror.
Oh ya.. and if thats not enough, browse the Verilog online, just in case your bored and feel like building one yourself. Download all the hardware goodies here, remember Niagara is GPLv2 and available via the OpenSPARC community.