You've got to check out Mike Day's insane BMX trial at the course being proto'd for the 08 Olympics in Beijing. Study this guy's rhythm through 32' gaps. Genius. Now while it may be impractical to go and source a BMX bike and try to get to your local huckin' course, you can gain SO MUCH for your cross game by getting in some BMX like practicing.
When you watch Sven, in the UCI leader kit in this video...
....you get a sense of why he won 8 Belgium BMX national titles back in the day. Frankly there's more impressive videos and photos of his bunny hopping and ditch hucking exploits, but this vid is nice to see some of the smoothness he has. Niels Albert ain't bad either. And while most of our courses here state-side do not have these meticulously inserted whoops (Faia, hook up those camel whoops at Breck this year!), you can be doing things rooted in BMX to practice and improve your cross game.
Some of the stuff I practice for goes back to my NBL days. When you set up your training barriers, consider doing this: Come at speed to the right (or left) of the barrier, do a HARD 180 back at the barrier, dismount/port/remount and once back on apply the sprint. I'll leave it up to you to figure out how many to do. Let's just say that I've got hours not minutes of this specific skill logged in already. It shoudl be in your stable.