Are there any rules concerning what I can put in my profile?
Generally speaking, your profile is (to an extent) fair game, as it is a reflection of you as a person, not the site as a whole.
There are reasonable limitations for all of those, but generally speaking, unless you're a hard-core spammer or you put something truly offensive / crazy in there (like hate speech or pornography), you'll be OK.
Also, understand that all links are no-followed, so SO doesn't actually give you Google Juice from your profile.
Your profile page is yours. You can put pretty much anything on there. But I wouldn't put the following:
Jeff covered some basics in this Meta answer.
Update: No, Profanity isn't removed. And there are always exceptions to the rule.