Alternatives to Hydrogen line frequencies

SETI and SETI League have been concentrating on using wavelengths believed to have universal significance to other civilizations, such as the so-called hydrogen-line frequency.

"Ice-cream truck" probes	Especially as seen in recent weeks and months we from earth have been "flooding" OUR solar system with probes. One possible SETI approach other civilizations could use might be probes that took meandering trips outward through various star systems, broadcasting signals targeted towards gaining the attention of anybody nearby happening to be listening. (remember when you were a kid and heard that ice-cream truck music wafting in from the distance ?) Signals from such a probe might be surprisingly strong and might appear suddenly on most any frequency and mode of modulation.
Low frequency broadcasts	While high frequencies have the benefit of inherantly higher energy levels, they have the disadvantage of extreme directionality. The image of a flashlight swinging in 3 dimensions from a string shows that even if we were momentarily pointed at some signal source, it might be just a passing signal which might never repeat again. If a civilization really wanted to, it could build large transmitting structures, for example on some moon with no atmosphere, and pump mega-watts (or better) out of it. The advantage of a low frequency would be that the long wavelengths might travel through obstacles that might otherwise be blocked, and it might not be directional at all. Heavy signal processing would probably be required to recover these beacons given all the natural noise at these frequencies.
???	I'm sure there must be other alternatives, including the (sounds like sci-fi to me) so-called "quantum" transmissions I've heard some allusion to, which would not be limited by light-speed.