With the assistance of Senator Jones, Mr. Obama helped deliver what is said to have been the first significant campaign finance reform law in Illinois in 25 years. He brought law enforcement groups around to back legislation requiring that homicide interrogations be taped and helped bring about passage of the state’s first racial-profiling law. He was a chief sponsor of a law enhancing tax credits for the working poor, played a central role in negotiations over welfare reform and successfully pushed for increasing child care subsidies.

NY Times

Sounds like an impressive record to me.  These, of course, are the high points to his State Senate career.  They're also bills that he sponsored.  A more complete record can be found here.  Some other high points in his voting record include raising the minimum wage, ending $300 million dollars in tax breaks for corporations, shielding workers from having overtime pay taken away, funding stem cell research, sponsoring a study of ways to implement universal healthcare, reducing the cost of prescription drugs, and unsuccessfully co-sponsoring a ban on discrimination based on sexual orientation (The measure became law after Obama was elected to the U.S. Senate).  DAMN impressive.