If you want to keep it totally separate, you probably just need another account. I have different settings for different friends, and you can limit what people can see (or respond to), but if you want to keep it completely separate then there's no other way to do it.
Well, I just checked, and it's a violation of their terms of use to get another facebook account. How do I set it up to have different settings for different friends. I've just been looking at it and have an idea, but are there easy ways to do it. I guess what I'm thinking is the whole News feed thing. If someone I know in real life comes and sees my profile and it says "posted ............. on ........... wall", that's not exactly what I want.
As others have said you can set different privacy settings for groups of friends. Eg. You can set your regular friends to see everything. But you can create another group for coworkers, bosses, teachers, relatives, trekbbs members, whatever that can only see your basic info. That way we won't see your drunken party pictures or anything else embarrassing your friends might post on your wall. (of course it would be more entertaining for Trekbbs members if you did not do this

)
But if that still doesn't satisfy you, just use a different email address to create another facebook account. Set up a new hotmail account or something.