Cross training athlete, running out of energy during long rides, what should I eat before I ride? I'm a high performance rower that uses cycling extensively to cross train (the local waterways are.....suboptimal some of the time).

When I'm out for longer rides (2-3hr) I generally run out of calories and crash, occasionally getting dizzy.  I've started carrying a camel pack and some snacks (granola, GU, etc.) which helps if the pack decides to stop for a quick pitstop but its often hard to get enough calories down fast without feeling it 10 minutes later.

I never have problems within my normal training but it typically never exceeds 2.5hrs and isn't quite as continuous.  Such a workout can easily burn 1500+ Cal, however.

My question is, is there anything I can eat before rides to maintain blood sugar levels so I don't pass out while trying to strike fear into the hearts of the local cyclists?
I don't know what you consider a "long ride" to be but I just did a 77 mile fund-raiser ride yesterday in Ohio. I averaged a little over 16mph for the entire ride. About 50 miles of the ride was into a 10-15 mph head-wind.

During the ride, I probably went through 10 large bottles of water and Gatorade, a dozen energy bars, a couple brownies and a Subway sub. The temperature was in the mid-80's with a little humidity. Even with all that, there were times I was a little light-headed and got some chills (almost a sure sign of not enough hydration). So on rides like this, you almost cannot drink and eat enough. It's very important you try though. If you don't, your body will let you know it, and you won't like how it feels :).

You don't necessarily need the pack to stop just to hydrate and eat. Most cycling jerseys have enough pockets to store a lot of energy bars and bottles of water. And you can probably include two bottles on your bike.