I mostly agree with Lauren Ipsum, just a couple of extra thoughts:
As Lauren says, John Doe and Jane Doe are widely recognized as fake names.
John Q Customer is often used for a fake customer name.
For US telephone numbers, use "555" for the exchange, like "123-555-1234". "555" is reserved by the phone companies just for use in examples and in books and movies. The other digits then don't matter: you can use a real area code or not.
Lauren mentioned using "example.com" for websites. This is also reserved specifically for examples, so you can be sure there will never be a real site with this name, and it's pretty obvious that it's an example.
I don't think there are any widely-recognized fake addresses. I generally use addresses that sound obviously fake, like "123 Some Street, Anytown PA 12345"
Definitely do not use any real person's information. Years ago I worked for a company that made a software package for doctors' offices, and at one point our chief marketing guy was going to some convention and he dropped by and casually asked me for a copy of a real customer's database that he could bring to the convention to use when giving demos of the product. I went through the roof. You want to use real people's private medical records for a demo at a convention?! I'm sure there are laws against that. Even if it was information not protected by law, you could set yourself up to be sued, or at the very least alienate customers with your lack of respect for privacy.
** Very late addendum **
The Social Security administration says that they will never assign numbers beginning 000, 666, or 900-999. So 000-00-0000 is good for examples and pretty obviously fake.
All the above said, note that people can be amazingly stupid and take examples for real. See http://www.ssa.gov/history/ssn/misused.html
If you use a real person's phone number, address, or social security number, there will be some number of people who will decide to call that phone number or try to use that social security number, and cause the real person all sorts of problems. If you make up a number at random, it is possible that it will by coincidence match a real person. Don't. A few years back I read that some developer was testing a system that sent automated emails, and so for test data he entered an email address by just mashing the keyboard. I forget what he said he came up with, but some totally random-looking, meaningless collection of letters.. Then he stuck "webmaster@" on the front and ".com" on the end. As there was no real organization with that email address, these emails were all returned and he used the error messages to verify that the correct emails had been sent. I'm sure you can guess where this is going. The test data was never deleted from the system, and a couple of years later a real company came along whose acronym just happened to match his random collection of letters. And they immediately started getting thousands of junk emails a day, and they were very unhappy.