I've been interested in the idea of space exploration for a long time myself, and I always wondered why operations weren't continued in regards to the moon. At our current level of technology we could have had a permanent settlement on the moon for years now. Also we could be mining asteroids in the near future for new and possibly invaluable minerals.
We could plant the seeds (so to speak) on mars by terraforming and in the distant future if we've raped the earth to the point that it's become unlivable then there is another option.