Justin Timberlake continues to be late-night ratings crack.  Timberlake visited Tonight Show Starring Jimmy Fallon last night; he and Fallon traveled back to the 90’s Camp Winnepesaukee again. Not coincidentally, the show delivered its top-rated night (3.5/9 in metered-market households) in nine months.  In adults 18-49 in the local people meters, it was the top Tonight (1.5/7) on a non-NFL night since Monday, March 24 (also a 1.5) and matched the show’s best night since Monday, March 3 (1.7). In Nielsen’s 56 metered markets, The Tonight Show Starring Jimmy Fallon delivered a household  3.5/9; CBS’s Late Show with David Letterman a 2.4/6; and ABC’s Jimmy Kimmel Live clocked a 2.0/5.  In the 25 markets with Local People Meters, Tonight also took the demo (1.5/7), trouncing Late Show (0.4/2) and JKL (0.6/3). Yes, some ratings credit also goes to Fallon’s guests Christoph Waltz and Nicki Minaj — and NBC’s The Voice finale.