A little more info for you:

There will be 3 chances to bet on the Derby future pool at your local racetrack/OTB.

Pool 1 Feb 8 (opens at 12 pm EST) - Feb 11 (closes at 6 pm EST)
Pool 2 Mar 8 (opens at 12 pm EST) - Mar 11 (closes at 6 pm EST)
Pool 3 Apr 12 (opens at 12 pm EST) - Apr 15 (closes at 6 pm EST)

These are the only days to place a future wager at your local racetrack/OTB. The final odds for each pool are set after betting closes on the final day of each pool. If you place your bet on Saturday and the odds are 25-1 on your horse, you are not assured of getting 25-1 odds. The final odds are displayed Sunday after the pool closes. Those odds will not change from that point on.

Each pool contains 23 individual betting interests, and a 'field' which includes every horse not listed (#24). The 'field' is a very popular wager, especially in Pool 1, since you get about 300 some horses. The field (#24) is the likely favorite in Pool 1.

As you get closer to the Derby (i.e. Pool 3), most of the horses likely to run in the Derby are identified. Generally speaking, it is less likely that a 'field' entry from Pool 3 will run in the Derby than from Pool 1 or 2.

If your horse does not run in the Derby (a very likely scenario), you lose. You do not get a refund. There is no cancelling your bet once it is placed.

It is possible to cancel a ticket if an error is made, but Churchill Downs is getting very selective in what is cancelled and why - basically if the teller screws up and you notice it immediately you stand a chance of getting a cancellation. If you walk away from the window, the ticket is yours.

Here is a link to the 'official' site of the 2007 Derby:

http://www.kentuckyderby.com/2007/

There you can find 'real time' odds, the final odds once the pool closes, and info on some of the top horses.