moss search does a pretty good job of doing partial as well as missspellings. it also has keywords where you can make a list of keywords and have it where if you put day, you can also put additonal words tied to it like dy daay da and it will know the person meant day. you can also do best bets where you can say if some search color piont them to this site on yellow.
this is all managed at the toplevel site under site actions site settings manage all site settins search keywords (under site collection administration)
