I also feel like I'm not very good at in-person interviews because I'm not very good on-the-spot. I mitigated this by using a variation of "The Briefcase Technique" which I learned from Ramit Sethi. The company I interviewed with is in the SAAS email space, so to get their attention I created a mini web app combining SMTP and web technologies. This took me about 3-4 hours tops. I was trying to demonstrate a few thing…
They also asked me lots of computer science oriented questions in the interview, and for most of them I just said, straight up, "I don't have a formal CS education, so I don't know, but here's how I think that works."
So many people try to stand out by doing some variation on the standard resume + cover letter routine, so it's relatively easy to stand out if you do literally anything else.