Cruise control is a basic measure for lead-footed drivers. The advanced hypermiling technique is called DWL - Driving With Load. In most situations, it is better than cruise control.
Say you are approaching an over pass (opposite of under pass :P). The cruise control reacts by opening the throttle more and/or downshifting on the climb, and upshifting/ closing the throttle downhill. This is not ideal for hypermiling.
You use DWL as follows. For cars without an iFCD (instantaneous fuel consumption display), don't change the throttle position you were using before the climb. The speed will fall slightly on the climb, and pick back up on the downhill.
If you the car has an iFCD (new Civic, City, Corolla), note your instantaneous consumption before the climb. Your goal is to maintain the consumption close to this value during the climb and the downhill. Again, the speed will fall and rise again.
For very steep slopes, pick a fuel consumption target such as 8-10 kml. Maintain it on the climb; shift to neutral on the downhill. Shift back into gear when finished. During the climb, don't downshift if you have a manual; try not to downshift if the car is automatic. It may go out of torque converter lock up, but that is still better than downshifting.
One slope I can think of is on M1, right before the Islamabad exit. Most cars are screaming at 5k+ rpm on this slope, and wasting fuel in the process.