The Film
The IMAX presentation of the "Price of Freedom" is shown several times a day just about 150 meters from the front door of the Alamo.  I recommend that all first time visitors go see this film.  It puts the whole Alamo story into a  prospective that is hard to come by in the urban setting it is in today.
Cost:  $9.65 per seat

The Book
If a picture is worth a thousand words then George Nelson's "The Alamo, An Illustrated History," is worth many times that.  Through much research Mr. Nelson gives you a birds eye view of the Alamo grounds through the ages with his drawings.  Actually I like his drawings better than the historical drawings and photographs used in the later part of the book.  Its a great book just to carry around the Alamo grounds as you try to imagine what it was really like in past times.  

I recently met Mr. Nelson at the Alamo gift shop.  He was holding court, signing books and telling tales of Texas.  Filling all the tourist with the "real" story of the Texas Revolution.  He was sincere, knowledgeable, and seemed to really enjoy interacting with the crowd.  
Cost:
$19.25 soft bound
$29.95 hard bound

The Ride
No trip to the Alamo City is complete without a ride on the San Antonio river courtesy of the folks at "Rio San Antonio Cruises". The cruises, about 1.5 miles and 45 minutes long, takes you around the horse shoe shape of the natural river bed, through the flood control channel dug in the 1930's, and along the newer man made sections put in for the 1968 Hemisfair and the River Center Mall.  
There are three places around the river  to catch a boat and they all return you to your starting point.  Just like a theme park you can have your picture taken just before boarding and the prints are ready upon your return.  The price of the pictures depend on whether you get just the 5 x 7 or get that and the picture on a key chain.  On the narrated ride where the "Captain" points out the building gargoyles, wedding island and the novelty of a tree growing through a wall, etc.
Cost: $6.50.  (Price updated 12/2004)

The Refreshment
After a hot day in San Antonio competing with the 25,000 other conventioneers, tourist, and history buffs for space, you will need some refreshments.  It's available from vending machines right behind the Alamo.  What is it?  "Agua del Alamo" of course.  Sucked right out of the Edwards Aquifer below and chilled for your pleasure.
Cost: $1.00