Yeah, Nuke Pulse is pretty inefficient. It is presently in a banned status, too, AFAIK.
My memory of Orion is shaky, but I seem to remember that you have to get it a good distance into space before you can even use the main engine, or face the prospect of nuking a good chunk of the area on launch (be it at ground zero or a high-altitude airburst, it's not going to be pretty).
Solar sails are nice to think about, but when you consider the sheer area of a sail to generate a decent velocity, it becomes a bit mind-boggling (as duestchland1 mentioned).
One idea that I've always had a pet interest in is the "fusion ramjet", a rocket which uses a giant magnetic "funnel" to suck up hydrogen and power a fusion engine. It's got the obvious benefit of not having to move the weight of it's own fuel and the equally obvious downside that, like Orion, it'll rip the planet a new one if you turn it on in-atmosphere).
I have a preference for Solar Sails and Bussard Ramjets, because those are the only propulsion systems hypothesized that take the reaction mass off the ship - in Solar Sails, it's the light or charged particles from an off-ship source(the Sun, or a big laser), and in Ramjets, it's hydrogen in the vacuum.
Unfortunately, we just don't have the engineering capacity for Bussard Ramjets at this time. The only non-FTL propulsion types I find truly capable of interstellar travel are Antimatter Drives and Bussard Ramjets, both of which are currently beyond what we can do now.
A Ramjet would need a freakin' utterly huge uber-powerful magnetic funnel and a way to fuse incoming hydrogen(not just deuterium, mind you) without slowing it down(because that would cause unacceptable drag). We haven't even been able to build a commercially reasonable fusion power plant yet(though ITER is on the job).
As for Antimatter Drives(I'm talking about pure Antiproton Annihilation Drives here, not Antimatter-Augmented Fusion or Antimatter Something-Core), they're the most powerful things that carry their reaction mass on board. But given that all the particle colliders in the world put together, working year round, can only generate enough antimatter to power a few light bulbs, these aren't going to be feasible anytime soon.
Solarsails are good for space travel within a solar system but outside it is where things get tricky, our sun ain't all powerful enough to supply ships lightyears away. It is cheap though since it doesn't actually use fuel, a ship with solarsails are most likely on the low end of maintainece costs.
Ramjets on the other hand are not very ideal, assuming that even with enough fuel floating about in space, we are still using fusion/fission based reaction. Not very good since the are the basic form of matter-energy transmutation.
Finally anti-matter drives, actually these babies stands a very good chance if we can somehow obtain enough anti-matter. Sure, we take forever just to gain enough from the colliders but there may be other ways as well. There is a good chance that somewhere outside in the universe that still contains isolated pockets of anti-matter, cross your fingers that they are close enough that we can actually harvest them. Still, I suspect that if enough research is done in the Quantum realm, they may be a chance to discover so called low-energy anti-matter production.
All of these drives are very useful to reduce the mass needed on spacecraft but they still don't solve the problem of sub-luminal travel. If each of these drives were to work somehow, we would face the prospect of cheap spaceships. Problem comes with travesing distance, even if ships were cheap, they would still take years, nay decades to reach anywhere outside the solarsystem.