For .co.uk domains you are able to "opt-out" of having your details readily available in the WHOIS database if you are an individual, as opposed to a business.
There is no such choice for .com domains, so your only option is to use a form of "proxy" registration, whereby you purchase the domain from a registrar who offers a service where they register the domain in their name on your behalf. Technically speaking this is a dodgy situation to be in (and as far as I'm aware ICANN do not support proxy registrations), but as long as you use a reputable registrar you should have no problems whatsoever, and you shouldn't come across any difficulties when you come to transfer the domain to a different registrar. Domain registrars do usually charge a premium for such services (most provide email forwarding facilities etc.), but it's unlikely to be more than the cost of the domain itself (<$10/year), and that's a small price to pay for your privacy in my opinion.
GoDaddy offer a service called
"Private Registration", Namecheap offer a service called
"WhoisGuard" and RegisterFly a service called
"ProtectFly". All are reputable registrars.
av.
Edit: You can always enter false information, and I'm sure someone will reply to this thread suggesting as much, but this violates ICANN regulations and leaves you open to having your domain taken off of you.