You've got to use an entirely separate browser for that IMO. Even with Chrome's totally segregated user profiles, it's too easy to pull up a NSFW URL in the wrong Chrome window and have it pollute your "work" profile.

I use FF for work and a special Chrome profile (not the default one) for anything that shouldn't pop up in my autocomplete in front of coworkers/clients.

That way it's pretty hard to screw up...