It's a big day for 500 Startups -- you know, the seed-stage accelerator and capital fund founded by rabble rouser and geek on a plane, Dave McClure. Back in July 2010, McClure filed for the accelerator's first fund, raising $30 million to begin officially investing in startups under the new venture capital fund. Today, we've learned via SEC regulatory filing that round two is officially on the books, and 500 Startups is going bigger for its second round, raising $50 million. McClure and company are also today announcing an expansion of the team, as Paul Singh and Christen O'Brien have been promoted to partners. Singh will continue to lead investments, running the accelerator program, and acting as head Data/Metrics guru, while O'Brien continues on her role as head of business development, leading events and conferences, like Geeks On A Plane, Warm Gun, etc. Bedy Yang and George Kellerman have also joined as venture partners. read more..