TV Top 5.

• Position: Living

"U.S. Open Tennis'' (12:30 p.m., Chs. 4 and 12) Women's semifinals and the mixed-doubles final in Flushing, N.Y.

"Stand Up to Cancer'' (8 p.m., Chs. 4, 5, 7, 10, 12, 22, 25, 64, 68, E!, FAM, FIT, FXM, HBO, LMN, OXY, TNT, VH1, ENCR, BRAVO, STARZ and NATGEO) Katie Couric hosts a fund-raiser for cancer research, featuring musical numbers by the Who, Jennifer Hudson, Lupe Fiasco, Common, Ariana Grande and Dave Matthews. Also appearing are Gwyneth Paltrow, Reese Witherspoon, Pierce Brosnan, Jennifer Aniston, Halle Berry, Jon Hamm, Ben Stiller, Will Ferrell, Mark Harmon, Rob Lowe, Jesse Tyler Ferguson and Eric Stonestreet.

"Four Weddings'' (9 p.m. and 11:02 p.m., TLC) A notorious film villain haunts a bride's Friday the 13th-theme affair, while guests bid bon voyage at a train station to a bride who loves to travel. Also: A baseball stadium offers terrific views; and a bride gets married at home plate.

"House Hunters'' (10 p.m. and 1 a.m., HGTV) A pair who work in television production decide to set up home base in Wilmington, N.C...