An ad from Target that tied into the finale of LOST and a summer-themed Walmart ad were the most liked and most recalled ads of the most recent period tracked by Nielsen.

The much-anticipated series finale of ABC’s LOST on May 23, which dominated blogosphere chatter and was the most-watched primetime program of the night with an average 13.6 million viewers, also delivered a highly engaging environment for its advertisers.

Recently, Nielsen launched the TV advertising effectiveness solution Nielsen IAG in the U.K. and published its inaugural U.K. data on the most memorable TV ads for the period Jan. 25 through Feb. 21.

The media has relentlessly covered the Tiger Woods story, but lately, Woods’ presence as product pitchman has been scarce. In addition to Tiger’s personal troubles, Nielsen data shows that brands associated with the golfing great are becoming part of the collateral damage.

Two commercials for Flomax topped the ranking of the most recalled drug/vaccine ads of the 2008-09 TV season, according to an analysis released by Nielsen.