The Great Train Expo will be at the National Western Complex on I-70 just east of I-25 in Denver on February 23 & 24, 2008. The Great Train Expo is a scale-model, modular layout show with a good number of exhibitors on hand each time they come through. The Colorado Rail Link layout has been a favorite of mine for a number of years.
For out-of-town visitors, the GTE site claims that if you mention "Great Train Expo" to the folks at Savannah Suites in Arvada, you can get a room for $69 per night, but a call today to their front desk at 720-889-2111 for a room with two double beds under that promotion yielded a price of $59.99 per night. There are likely other deals to be had elsewhere too.