the main benefit of consolidating federal loans is to lower your monthly payment. if you have older federal loans they may still have a variable interest rate in which case consolidating those will fix in the rate. consolidating does not save you money if you take the full 20+ years to pay it. It just saves you initially on the monthly payments.
federal and private loans cannot be consolidated together, I also do not know of any company that does both, even separately. Direct loans is the only place I know of that consolidates Federal loans. (1800-557-7392)...or dlssonline.com
Wells Fargo is the only place I know of that consolidates private loans....1800-658-3567...benefit of consolidating private loans is lower monthly payment...and in a perfect world, lowering your interest rate as well.
So to answer your shopping question...these days with this economy...you dont have many options...the 2 above are all ive got