Lenny Kravitz and Yankees slugger Alex Rodriguez are the latest celebs urging fans to help the people of Haiti rebuild after Tuesday's devastating earthquake.

"Our neighbors in Haiti are in desperate need of our help in their darkest hour," Kravitz, 45, says in an exclusive UsMagazine.com clip promoting SaveHaitiSaturday.com, which encourages businesses to donate a portion of their earnings on that day to the relief effort.

"We have to band together as one to help our Haitian brothers and sisters," he continues. "Time is of the essence."

Alex Rodriguez also supports the Haiti relief effort. (His ex Madonna announced a $250,000 donation earlier Friday.)

HOW YOU CAN HELP: Log onto SaveHaitiSaturday.com or text BEST to 501501 to donate $5 to relief efforts.