Unless something happens in the last two months of this year, 2008 will be the warmest La Nina-influenced year discounting 1998, a year that was split between La Nina and an even stronger El Nino.
The list of El Ninos and La Ninas is here, with recent La Ninas in 2008, 2000, 1999, 1998, and 1995 (prior La Nina years weren't nearly warm enough to compete). This graphic shows how 2008 is stacking up so far, while this chart shows temperatures for 1880-2007. Eyeballing the graphic to 2000, 1999, and 1995 shows this year trending towards being warmer than the others.
Another way to consider it is to use the first link and scroll to the bottom for years that only had La Nina and no El Nino events: this year (probably), 2000, 1999, 1971, 1974, and 1975 (and a few earlier ones). This year's on track to be the warmest year in the instrumental record with La Nina and without El Nino.