Can I but an iPhone 5 without a plan/ carrier?

Not yet, unlocked iPhone 5 was not announced yet

Of course you can. Pre-order in the Apple Store

Well actually, no you can't, because all the iPhones for sale are linked to the three carriers - you can't purcahse the unlocked iPhones, unless you go for a 4s, which is probably not a good idea with the iPhone 5 coming out.

Unlocked phones are not yet available on the online U.S. Apple Store.

Ah, I just thought...you must be talking about the U.S.

We can all buy the unlocked iPhone 5 already in the UK

The OP wasn't specific

default US 😉

We need to change that I think 😉

Dream on..........................

you can buy the non commitment price on ATT which is without contract, , then ask them to unlock it. However you have to be their previous customer.

here is on the eligiblity of unlocking iphone:

General eligibility requirements for unlocking iPhone

AT&T will unlock an iPhone under the following circumstances:

• The person requesting the unlock is:
  • A current AT&T customer.
  • A former AT&T customer who can provide the phone number or account number for the account.
• The iPhone was designed for use on the AT&T network.
• All contract obligations, including any term commitment, associated with the device to be unlocked have been fully satisfied.
• The iPhone has not been reported lost or stolen.

Additional information about iPhone unlocks

(ii) a person who purchased the iPhone from an authorized location at the "no commitment" price and can provide proof of purchase.

When will we be able to buy it from Apple without a contract? Any guesses?

I would guess when Apple decide they are ready to sell unlocked iP5

I am sure they will tell us all when they make the decision

In the mean time we do not speculate on this forum 😉