For situations that require a change of direction, say from directly downstream to directly across or anywhere between, I've come to rely on a single or double spey cast done with the single handed rod. You won't, of course be able to handle as much line as you could with the longer spey rod but it allows for a ninety degree change of direction with a single (in the case of the single spey) smooth motion. I usually strip the fly in until I have twenty to thirty feet of line out, go through the motions, make one false cast if necessary and shoot line into the final cast. It gets the fly back into (or onto) the water quickly with a minimum of false casting.
The one cast that I find invaluable for fishing moving water, particularly with dry flies, is the reach cast (sometimes called the reach mend). Cast across stream (or slightly upstream or downstream, depending on the current) and shoot a bit of line into the cast. As soon as the line (the portion you're going to shoot) is released by the left hand, move the rod tip upstream as far as possible. In effect you are making an upstream mend while the line is in the air. The direction of the fly has already been determined when the cast was made and before the shooting line was released. As the fly touches down, bring the rod tip back downstream to maintain a controlled amount of slack as the fly floats down the current. Sounds pretty complicated when described in words but it seems to come pretty naturally when you're actually casting.
