It depends on the type of student loans you have. For graduate school, I had to take out a private loan (~12,000) with Sallie Mae. Because my credit score at the time was quite poor, my interest rate was about 14%! Since I finished school in December, I found out about an organization called Graduate Leverage (http://graduateleverage.com). I consolidated my Private Loans through them through a company called Meritas. With an improved credit score, and a my wife as a co-signer, my interest rate is about 7.8%!!!!
I'd definitely recommend Graduate Leverage. They also do Federal Loan consolidation. Send me a message if you have any questions!