I've been studying German throughout high-school and college. I am about to hit the workforce and am open to living almost anywhere in the US. I am interested in hearing about possible means of turning a skill in German (or, in general, a language) into employment. For instance, how feasible is it to be a teacher with only a college diploma? Is there a demand for translators?
That depends a bit on how good your German is. For a teacher it's typically a good idea to be a native speaker or close to the native level. Our German-born kids took German in a US high school but we quickly pulled them out since the teacher's German was really quite bad and the classes did more damage than good.
You can also specialize in business German, German literature, technical German, bio-tech German, etc. Specialization can really help you get a job: as a negotiator, technical writer, translator, pharma rep, etc.
The best way to learn the language to an advanced level is to immerse yourself in it. You can consider doing an internship in Germany where you speak German 24/7 and where you can also do specializations on the job. It's actually not that hard for an US citizen to get an internship in Germany (the other way around is a different story).