Back-to-back natural disasters in Mexico and across the Caribbean have left millions of people reeling.The 7.1 magnitude earthquake that struck central Mexico on Tuesday crumpled buildings and killed more than 200 people. And it hit while Mexico was still recovering from another deadly and powerful earthquake in the southern part of the country. On Thursday rescue workers were still trying to free trapped victims.On Wednesday Hurricane Maria dealt Puerto Rico a direct punch, knocking out power across the entire island. Its rains have led to widespread flooding and its heavy winds took roofs, snapped power lines and uprooted trees. "The Puerto Rico and San Juan we knew yesterday is no longer there," Mayor Carmen Yulín Cruz told NBC News.Other parts of the Caribbean have had no time to catch their breath after surviving Hurricane Irma only to be ravaged by Maria.As crews attempt to clean up and distribute aid, Kenneth Mapp, governor of the U.S. Virgin Islands, issued a 24-hour curfew on Thursday. And the Associated Press reports that Maria left at least nine people dead in Dominica and Guadeloupe.NPR's Jason Beaubien spent time on the U.S. Virgin Islands after Irma hit and reports, "St. Thomas was basically surviving on a lifeline out of St. Croix and Puerto Rico and that lifeline was severed by Maria."Beaubien advises against volunteers traveling to the region to help rebuild, noting that just getting enough clean water on the islands is "a huge problem, so extra bodies will need access to clean water too."There are other ways to extend a lifeline. Here are some charities with an on-the-ground presence and accepting donations:CaribbeanMy Brother's Workshop is a St. Thomas-based charity that has been running a daily lunch program on the island.Americaresdelivers medicine and aid to local health providers and is readying emergency kits for future crises.GlobalGiving is supplying emergency supplies across the Caribbean in addition to longer-term recovery help.All Hands Volunteers is a volunteer-driven disaster relief organization awaiting "the green light" from first responders to get back to St. Thomas to help.Catholic Relief Services is working with local governments across the Caribbean to provide relief including shelter, water and kitchen kits to hurricane victims.The Florida-based National Puerto Rican Leadership Council Education Fund is helping coordinate relief efforts. President Carlos Guzman tells NPR they are accepting diapers, formula and water. But he adds, "money is better because all the airports are shut down," and the group is trying to get goods over the island via private jets.MexicoTopos México, an all-volunteer rescue brigade, is working to dig out victims and is accepting support. Donation information is on their Twitter page.The Mexican Red Crossor Cruz Roja Mexicana has teams assisting in search and rescue operations. It has also put togetheran Amazon wish list of needed items, including tents, baby supplies and batteries.Oxfam is asking for funds as it develops a response plan in coordination with the Mexican government and other aid organizations.Save the Children is raising money for a children's relief fund.How to make your money go further"As when giving with any charity, try and do your due diligence about the organization you are giving to. Do friends vouch for it? Has it been endorsed by other trustworthy organizations? And watch out for scams," reports NPR's Carrie Kahn from Mexico City.A good place to start is by looking up charities at Charity Navigator or Guidestar. Both are themselves charities that evaluate other nonprofits and track where their money goes. Copyright 2017 NPR. To see more, visit http://www.npr.org/.