Apparently federal student loan interest rates are going to increase July 1, so if you want to lock in the lower interest rate, you have to consolidate your loans before then.  I used Graduate Leverage last year (they do collective bargaining for graduate students and get the lowest rates I've heard of) and really liked them, and they got me a really low interest rate this year too.  I thought I'd pass the website along--they have super helpful customer service people who can explain all the pros and cons, but you still get deferrment (so you don't lose your grace period if you just graduated) and there aren't prepayment penalties.

www.graduateleverage.com