With all of the patents out there, what is the best way to figure out which features I've added might infringe on a patent/idea I've never heard of?
Well. First IANAL. But from my understanding you are better off moving forward without researching patents in depth. Obviously if you depend on a specific algorithm used in a specific way you should likely validate you are free from incumbencies. But outside of that you are safer not looking up patents because you can claim you had no knowledge and invented it on your own. While maybe not a saving factor in the end it can save you significant legal consequences.<p>Of course when in doubt an attorney has his/her usages. Also others here may have better or more experience.
Given the way that software patents work, you probably are.<p>But for the vast majority of startups, this is not something you should be worrying about early on. Let the lawyers sort it out later during due diligence. Worry about getting customers first. You should consult your legal counsel (rather than the internet) about your specific case, but in general...build the damn thing and start selling it, instead of looking for excuses not to.