It looks like this thread is pretty well on track! I just want to verify a few things and answer a few questions and comments:

Standalone Licenses - Licensing twice

The licensing agreement reads:

Additional Installation: Except with Educational, Student and Evaluation Versions, you may make a second copy of the Software on the hard disk of a second computer owned by you or under your control provided that (1) the original and second copies are used only by the same person; (2) the second copy is installed and used only on either (i) with respect to Network Versions, a redundant server that makes the Software available for use only when your primary server on which the Software is installed becomes inoperable, or (ii) a notebook computer, home computer, or other non-server computer away from your usual work location for the purpose of enabling you to perform work while away from your usual work location; (3) only one of the Software copies is in use at any one time; (4) the second copy of the Software is used exclusively with the copy protection device (if any) supplied with the Software, and (5) the Software is not licensed and/or labeled as an Educational Version or Student Version.
I'm no lawyer, but in summary you can license Revit on a second machine if you are in control of that machine and do not use Revit on the two machines concurrently. There's a bit more to it than this, but for the purposes of this thread, that should answer the question on stand-alone usage and licensing the software on multiple machines.

Standalone Licenses - Moving your license

If you need to move your license from one machine to another, you can use the Portable License Utility (PLU). This will disable Revit on the machine from which the license is "borrowed" and enables it on the "borrowing" machine. This is pretty well documented in help, and PeterJ summarized it pretty well earlier in this thread.

IMHO - this functionality provides greater flexibility than was available to users prior to 6.0 (and 5.1L).

Network Licensing - Borrowing

Scott nailed this one on the head...

If you are on a license server, you can check out a license for a period of time, using the License Borrowing Utility located in the Start Menu>Programs>Autodesk Revit 6.0

Couple of draw backs: The computer to want to 'borrow' a license for, must be on the network where the license server resides. You can't 'borrow' to a disk, take it home, pop it in and go. Once you borrow a license, it will revert back in the number of days you choose. But you will have one less available for that time frame on your license server. You can have an 'Early check-in' which will put the license back on the license server before the time is up.
Again IMHO - this is an increase in flexibility to the prior licensing method (5.1 and earlier).

Replies to some specific questions / comment:

pashley - So the answer to your 1st questions is "Yes" on all accounts (assuming you have Stand-alone licenses).

mlgatzke - I'm not an ACAD expert, but I do not believe the Server allows you to check a license out without the physical device (computer) actually being on network during checkout. Feel free to double check this on the autodesk.autocad.network newsgroup.

sfaust - You need to acquire a new Authorization Code to license on the new machine. You can (and will need to) use the same serial number on the new computer, which will result in a new/different request code, to acquire the new authorization code. The serial number and your computers unique "signature" combine to create a unique request code which, in turn, returns a unique Auth Code.

pashley - Prior to 6.0 (5.1L) there was no such thing as a Portable License Utility in the terms it is being used today. You were permitted to install and license Revit on two machines... that has not changed, and it will not count against your totals if you do so. In addition to that, now you can move that license from/to any computer at your discretion using a tool called the Portable License Utility. In the past, once you licensed on your "transfer" computer, and wanted to move the license again, you had to call Revit Support and get us to clear your license.