First of all congratulations for having a long-term plan. You know where you want to end up. That's big. And you're flexible enough that it can be a startup or a prestige company.
Micro-apps. Build something small like a Twitter visualization (twistori.com was built in a day, twittervision.com in 4 hours!), release it, build a blog to record your projects.
And I'd like to suggest broadening your portfolio: If it's all technology, it's all in one basket. Entrepreneurship is about taking on and managing risk. Outside the controlled world of compilers and stack traces, there is opportunity.
Consider taking on activities of varying risk. What are you scared at getting better at? Does it scare you to give a presentation? Join Toastmasters. Or ask a question at the microphone in a public forum (that's p.s.) Does it scare you to mingle in a room of strangers? Get a group of guy friends and go practice. Nothing to lose. Or start by going to a lecture and talking with the person you sit down next to. Does not having control scare you? Mentor or tutor a teenager. Or be the new guy in an interest group.