+1 to what CnC posted.
Most CU's and also some other institutions (USAA / Wells Fargo) will offer this service and I highly recommend it. CU loan limits are around 1K typically though I believe there was a $500 one floating around, USAA is 2.5K and Wells is 3K last I checked.
Personally I went with USAA's as it was directly tied to a CD and I could specify the term on it, I wanted longer than a year that some of the other secured loans do. It was a straight benefit to my credit report, but I only had one other installment loan ever on my report, if you have a thicker file with regards to installment loans, it likely won't be as beneficial.
Also, moving this post 
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Starting Score: EQ 561, TU 567, EX 599* (12/30/11, EX lender pull 12/29/11)Current Score: EQ 660, Wally TU 697, EX unknown (05/13/13)
Goal Score: 680 in all three (01/01/14)
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