Try google "NSLU2" - and discover how the next 2 hours feels like minutes! Information about this device never stops.. (which is fantastic!)
The trick however, is to find that particular guide that really satisfy your geeky needs.
Of course there is NSLU2-linux.org which contain a bunch of goodies. But if you want an easy to read introduction "guide" and learn what the NSLU2 is capable of, I recommend this one.
Besides the original linksys firmware. There are different distributions to the slug that you can play with. Read about them right here.
If unslung was your decision. I recommend you try the guides on this blog starting from the beginning.
Personally I did not accomplish getting the Unslung v.6.10 to spin down my disks. Using the v.5.5 however gave a positive result. If anyone did succeed, please let me know how! Cause no1 else seems to know how to get v6.10 spinning down those hardworking harddrives.
I will try to experiment with the other distros and let you know if I succeed right away! Of course useful guides will be produced if I succeed. Nslu2 For the win! :)
see the new debian guides for a successful spindown rush! ;)