My fellow blogger hilzoy of Obsidian Wings summarized Obama's legislative approach this way:
His bills tend to have the following features: they are good and thoughtful bills that try to solve real problems; they are in general not terribly flashy; and they tend to focus on achieving solutions acceptable to all concerned, not by compromising on principle, but by genuinely trying to craft a solution that everyone can get behind.
Moreover, hilzoy continues, "His legislation is often proposed with Republican co-sponsorship." This is a good thing. This is a way to get legislation actually passed. His work with Sen. Dick Lugar, one of the real statesmen of the Republican Party, on securing loose nuclear weapons is an excellent example of Obama's approach. His work on getting an ethics bill that could actually pass is another. And preparing for avian flu. And regulating genetic testing. And making a federal database of political contributions. Etc, etc.
A legislator's record includes what they did when not in office. When Obama finished his fancy education at Occidental, Columbia, and Harvard Law, he did not just go corporate and cash in. He went to the slums to work with poor people to organize their communities, so that they could make their own lives better. That is about as Gen X (and centrist) a form of giving back as you could name. (And let me be quick to say that Sen. Clinton's service to poor women, and Sen. McCain's military service, when they were done school are equally honorable - a stark contrast with the current president's twenties. And thirties.)
Senator Obama's record as a legislator is a solid roster of working with the other side to achieve worthwhile things. You might oppose what Obama wants to do as president, but it would be unfair and ill-informed to say that he hasn't really done anything.